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Scope and Delimitations – Explained & Example

• By DiscoverPhDs
• October 2, 2020

What Is Scope and Delimitation in Research?

The scope and delimitations of a thesis, dissertation or research paper define the topic and boundaries of the research problem to be investigated.

The scope details how in-depth your study is to explore the research question and the parameters in which it will operate in relation to the population and timeframe.

The delimitations of a study are the factors and variables not to be included in the investigation. In other words, they are the boundaries the researcher sets in terms of study duration, population size and type of participants, etc.

Difference Between Delimitations and Limitations

Delimitations refer to the boundaries of the research study, based on the researcher’s decision of what to include and what to exclude. They narrow your study to make it more manageable and relevant to what you are trying to prove.

Limitations relate to the validity and reliability of the study. They are characteristics of the research design or methodology that are out of your control but influence your research findings. Because of this, they determine the internal and external validity of your study and are considered potential weaknesses.

In other words, limitations are what the researcher cannot do (elements outside of their control) and delimitations are what the researcher will not do (elements outside of the boundaries they have set). Both are important because they help to put the research findings into context, and although they explain how the study is limited, they increase the credibility and validity of a research project.

Guidelines on How to Write a Scope

A good scope statement will answer the following six questions:

• Why – the general aims and objectives (purpose) of the research.
• What – the subject to be investigated, and the included variables.
• Where – the location or setting of the study, i.e. where the data will be gathered and to which entity the data will belong.
• When – the timeframe within which the data is to be collected.
• Who – the subject matter of the study and the population from which they will be selected. This population needs to be large enough to be able to make generalisations.
• How – how the research is to be conducted, including a description of the research design (e.g. whether it is experimental research, qualitative research or a case study), methodology, research tools and analysis techniques.

To make things as clear as possible, you should also state why specific variables were omitted from the research scope, and whether this was because it was a delimitation or a limitation. You should also explain why they could not be overcome with standard research methods backed up by scientific evidence.

How to Start Writing Your Study Scope

Use the below prompts as an effective way to start writing your scope:

• This study is to focus on…
• This study covers the…
• This study aims to…

Guidelines on How to Write Delimitations

Since the delimitation parameters are within the researcher’s control, readers need to know why they were set, what alternative options were available, and why these alternatives were rejected. For example, if you are collecting data that can be derived from three different but similar experiments, the reader needs to understand how and why you decided to select the one you have.

Your reasons should always be linked back to your research question, as all delimitations should result from trying to make your study more relevant to your scope. Therefore, the scope and delimitations are usually considered together when writing a paper.

How to Start Writing Your Study Delimitations

Use the below prompts as an effective way to start writing your study delimitations:

• This study does not cover…
• This study is limited to…
• The following has been excluded from this study…

Examples of Delimitation in Research

Examples of delimitations include:

• research objectives,
• research questions,
• research variables,
• target populations,
• statistical analysis techniques .

Examples of Limitations in Research

Examples of limitations include:

• Issues with sample and selection,
• Insufficient sample size, population traits or specific participants for statistical significance,
• Lack of previous research studies on the topic which has allowed for further analysis,
• Limitations in the technology/instruments used to collect your data,
• Limited financial resources and/or funding constraints.

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Research Limitations & Delimitations

What they are and how they’re different (with examples)

By: Derek Jansen (MBA) | Expert Reviewed By: David Phair (PhD) | September 2022

If you’re new to the world of research, you’ve probably heard the terms “ research limitations ” and “ research delimitations ” being thrown around, often quite loosely. In this post, we’ll unpack what both of these mean, how they’re similar and how they’re different – so that you can write up these sections the right way.

Overview: Limitations vs Delimitations

• Are they the same?
• What are research limitations
• What are research delimitations
• Limitations vs delimitations

First things first…

Let’s start with the most important takeaway point of this post – research limitations and research delimitations are not the same – but they are related to each other (we’ll unpack that a little later). So, if you hear someone using these two words interchangeably, be sure to share this post with them!

Research Limitations

Research limitations are, at the simplest level, the weaknesses of the study , based on factors that are often outside of your control as the researcher. These factors could include things like time , access to funding, equipment , data or participants . For example, if you weren’t able to access a random sample of participants for your study and had to adopt a convenience sampling strategy instead, that would impact the generalizability of your findings and therefore reflect a limitation of your study.

Research limitations can also emerge from the research design itself . For example, if you were undertaking a correlational study, you wouldn’t be able to infer causality (since correlation doesn’t mean certain causation). Similarly, if you utilised online surveys to collect data from your participants, you naturally wouldn’t be able to get the same degree of rich data that you would from in-person interviews .

Simply put, research limitations reflect the shortcomings of a study , based on practical (or theoretical) constraints that the researcher faced. These shortcomings limit what you can conclude from a study, but at the same time, present a foundation for future research . Importantly, all research has limitations , so there’s no need to hide anything here – as long as you discuss how the limitations might affect your findings, it’s all good.

Research Delimitations

Alright, now that we’ve unpacked the limitations, let’s move on to the delimitations .

Research delimitations are similar to limitations in that they also “ limit ” the study, but their focus is entirely different. Specifically, the delimitations of a study refer to the scope of the research aims and research questions . In other words, delimitations reflect the choices you, as the researcher, intentionally make in terms of what you will and won’t try to achieve with your study. In other words, what your research aims and research questions will and won’t include.

As we’ve spoken about many times before, it’s important to have a tight, narrow focus for your research, so that you can dive deeply into your topic, apply your energy to one specific area and develop meaningful insights. If you have an overly broad scope or unfocused topic, your research will often pull in multiple, even opposing directions, and you’ll just land up with a muddy mess of findings .

So, the delimitations section is where you’ll clearly state what your research aims and research questions will focus on – and just as importantly, what they will exclude . For example, you might investigate a widespread phenomenon, but choose to focus your study on a specific age group, ethnicity or gender. Similarly, your study may focus exclusively on one country, city or even organization. As long as the scope is well justified (in other words, it represents a novel, valuable research topic), this is perfectly acceptable – in fact, it’s essential. Remember, focus is your friend.

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Conclusion: Limitations vs Delimitations

Ok, so let’s recap.

Research limitations and research delimitations are related in that they both refer to “limits” within a study. But, they are distinctly different. Limitations reflect the shortcomings of your study, based on practical or theoretical constraints that you faced.

Contrasted to that, delimitations reflect the choices that you made in terms of the focus and scope of your research aims and research questions. If you want to learn more about research aims and questions, you can check out this video post , where we unpack those concepts in detail.

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This post was based on one of our popular Research Bootcamps . If you're working on a research project, you'll definitely want to check this out ...

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18 Comments

Good clarification of ideas on how a researcher ought to do during Process of choice

Thank you so much for this very simple but explicit explanation on limitation and delimitation. It has so helped me to develop my masters proposal. hope to recieve more from your site as time progresses

Thank you for this explanation – very clear.

Thanks for the explanation, really got it well.

This website is really helpful for my masters proposal

Thank you very much for helping to explain these two terms

I spent almost the whole day trying to figure out the differences

when I came across your notes everything became very clear

thanks for the clearly outlined explanation on the two terms, limitation and delimitation.

Very helpful Many thanks 🙏

Excellent it resolved my conflict .

I would like you to assist me please. If in my Research, I interviewed some participants and I submitted Questionnaires to other participants to answered to the questions, in the same organization, Is this a Qualitative methodology , a Quantitative Methodology or is it a Mixture Methodology I have used in my research? Please help me

How do I cite this article in APA format

Really so great ,finally have understood it’s difference now

Getting more clear regarding Limitations and Delimitation and concepts

I really appreciate your apt and precise explanation of the two concepts namely ; Limitations and Delimitations.

This is a good sources of research information for learners.

thank you for this, very helpful to researchers

Very good explained

Great and clear explanation, after a long confusion period on the two words, i can now explain to someone with ease.

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Scope and Delimitations in Academic Research

Table of contents

• 1.1 Examples of Elements Included in the Scope
• 2.1 Examples of Delimitations in Research
• 3 Determining the Scope and Delimitation
• 4 Writing the Scope and Delimitations Section
• 5 Conclusion

Understanding the scope and delimitations of a study is crucial for defining its parameters and ensuring focused research efforts. What are delimitations in a research study? These components establish the boundaries within which the research will operate and clarify what the study aims to explore and achieve. This article delves into the significance of clearly defining the scope and every delimitation, how they guide the research focus, and their roles in shaping the research process. Additionally, it provides insights into determining these aspects and articulating them effectively in a research proposal or paper. Transitioning smoothly into the main discussion, let’s explore the importance of scope in research, guiding the focus.

The importance of Clearly Defining the Scope of the Study for Guiding Research Focus

The scope of research delineates its extent or range of inquiry, setting clear parameters for what the study will cover. It’s a foundational aspect that guides every step of the research process, from the formulation of research questions to the interpretation of results. Defining the scope helps in focusing the research efforts, ensuring that the study remains manageable and within realistic bounds.

Understanding the scope and limitation of the study allows researchers to allocate resources efficiently, ensuring that every aspect of the study receives adequate attention. It also helps in avoiding the common pitfall of overreaching, which can dilute the research’s impact and make findings less actionable. By setting a defined scope, researchers can more easily communicate their work’s relevance, limitations and delimitations in the research process to stakeholders, enhancing the credibility and applicability of their findings. Furthermore, a well-defined scope can facilitate a more targeted and effective literature review, laying a solid foundation for the research study.

When navigating the complexities of defining a study’s scope, researchers might seek external support to ensure their research is concise, well-structured, and impactful. A writing service , PapersOwl offers a spectrum tailored to meet academic research’s unique demands. Their expertise can be particularly beneficial in refining research proposals, ensuring the scope is clearly communicated and aligned with academic standards. Engaging with such a service allows researchers to benefit from professional insights, which can enhance the coherence and focus of their work. This collaboration can be instrumental in identifying the most relevant study areas and avoiding unnecessary diversions. With PapersOwl’s support, researchers can ensure their project’s scope is well-defined and compellingly presented, making a strong case for its significance and feasibility. This partnership can be a strategic step towards achieving a study’s specific objectives, ensuring it contributes valuable insights within its defined boundaries.

Examples of Elements Included in the Scope

Defining the scope of a research project is akin to drawing a map for a journey; it outlines the terrain to be explored and the boundaries within which the exploration will occur. This clarity is essential for guiding the research process, ensuring the investigation remains focused and relevant. The scope encompasses various elements, each contributing to the overall direction and integrity of the study. Let’s delve into some of these key elements:

• Research Objectives : The specific aim the study is designed to achieve.
• Geographical Coverage: The physical or virtual locations where the research is conducted.
• Time Frame: The period during which the study takes place, which could range from a few days to several years.
• Subject: The specific topics or issues the research intends to address.
• Population Being Studied: The group of individuals, organizations, or phenomena being investigated.

These components of the scope serve as critical navigational tools in the research journey. They ensure that the study remains grounded in its objectives, relevant to its intended audience or population, and manageable within its temporal and geographical constraints. By carefully defining these elements at the outset, researchers can avoid common pitfalls such as scope creep, where the study’s focus broadens uncontrollably, potentially diluting its impact and significance. A well-defined scope is instrumental in crafting a focused, coherent, and impactful research project.

Role of Delimitations in Qualitative Research

Delimitations in research examples specify the boundaries set by the investigator on what the study will not cover, distinguishing them from limitations, which are potential weaknesses in the study not controlled by the researcher. Delimitations are choices made to narrow the scope of a study, focusing on specific aspects while excluding others. In the intricate tapestry of research design, delimitations play a pivotal role in sharpening the focus and enhancing the clarity of a study. By explicitly stating what the research will not explore, delimitations help prevent the dispersion of the research efforts across too broad an area, thereby increasing the depth and specificity of the investigation. This strategic narrowing allows researchers to concentrate their inquiries on areas most likely to yield impactful insights, making efficient use of available resources and time.

One might wonder how to establish these boundaries effectively without compromising the potential breadth of discovery. Here, the expertise provided by platforms like PapersOwl, particularly their research paper help service, becomes invaluable. Their seasoned professionals can offer guidance on crafting a research design that is both focused and flexible, assisting in identifying and justifying delimitations that enhance the study’s relevance and feasibility. Through such collaboration, researchers can balance the scope and delimitation of the study, ensuring that it remains grounded in its objectives while open to unforeseen insights.

Furthermore, acknowledging delimitations in a research paper demonstrates a researcher’s critical understanding of their study’s context and constraints, enhancing the credibility of their work. It shows a mindful engagement with the research process, recognizing that by setting deliberate boundaries, the study can delve more deeply and meaningfully into its chosen area of inquiry. Thus, when thoughtfully articulated with support from research paper writing help, like that offered by PapersOwl, delimitation in research becomes a testament to the rigor and integrity of its effort.

Examples of Delimitations in Research

Delimitations in research are akin to the guardrails on a highway; they keep the investigation on track and prevent it from veering into less relevant or overly broad territories. Below are some examples of how researchers can apply delimitations to fine-tune their investigations:

• Restricting the Study to Certain Age Groups: Focusing on a specific demographic, such as teenagers or the elderly.
• Geographic Locations: Limiting the research to a particular country, city, or region.
• Specific Periods: Studying a phenomenon during a particular time frame, ignoring other periods.

Setting these research delimitations is not about narrowing the vision of the research, but rather about sharpening its focus. It allows for a more thorough and nuanced exploration of the chosen subjects, leading to more precise findings and general delimitation meaning in research. Delimitations highlight the researcher’s awareness of the study’s scope and commitment to conducting a focused, manageable investigation.

Determining the Scope and Delimitation

Identifying the scope and delimitations of your research involves understanding the research problem deeply and recognizing what is feasible within the constraints of time, resources, and data availability. Strategies for determining these include:

• Reviewing existing literature to identify gaps and opportunities.
• Consulting with experts or advisors to refine research questions.
• Considering data availability and methodological constraints.

Balancing the scope and delimitations involves ensuring the research is neither too broad, unmanageable, nor too narrow, limiting its significance. Crafting a research project that strikes the right balance between breadth and depth is a nuanced task. It requires a researcher to be acutely aware of where their study begins and ends, what it encompasses, and what it intentionally leaves out. This equilibrium is not found in isolation but through a diligent exploration of the field and an understanding of how to best position one’s work within it. A key step in this process is identifying and sourcing relevant literature and data, which can significantly influence the scope of research.

Leveraging resources such as PapersOwl’s guide on how to find sources for research papers can prove invaluable in this phase. This platform provides insights into locating credible and relevant information, ensuring that researchers build their work upon a solid foundation of existing knowledge. By understanding how to navigate the vast, effective ocean of available data, researchers can make informed decisions about the direction and limits of their study. This meticulous preparation is crucial for defining the scope and delimitations and justifying them within the context of the research proposal or paper. It demonstrates a researcher’s commitment to rigor and depth, showing that their choices are informed by a comprehensive understanding of the subject and its existing body of literature.

Writing the Scope and Delimitations Section

Articulating the scope and delimitations in a research paper or proposal is crucial for setting clear expectations. It should clearly define delimitations and what the study will and will not cover, providing a rationale for these choices. Effective wording and structure involve:

• Stating the research objectives and questions upfront.
• Describing the research methodology , data collection methods and analysis.
• Outlining the geographical coverage, time frame, and subject matter.
• Clearly stating the delimitations and the reasons behind them.

The presentation of the scope and delimitations within a research document not only guides the readers through the intentions of the research but also establishes a framework for evaluating the findings. It’s a critical section where transparency and precision are paramount, allowing the audience to grasp the extent of the study and the rationale behind its boundaries. This transparency is essential for the credibility of the research, as it demonstrates a conscious and deliberate effort to focus the investigation and acknowledges the existence of boundaries that the study does not cross.

To ensure clarity and impact, this section should seamlessly integrate with the overall narrative of the research proposal or paper. Researchers are advised to avoid jargon and overly technical language, making the research scope and delimitations accessible to a broader audience. This includes a layperson who may not have deep expertise in the field but an interest in the study’s outcomes. Additionally, it is beneficial to highlight how the defined study scope and delimitations contribute to addressing the research problem, filling knowledge gaps, or exploring uncharted territories.

Moreover, this part of the document offers an opportunity to discuss how the chosen delimitations enhance the study’s focus and depth. By justifying the exclusions, researchers can address potential critiques head-on, reinforcing the methodological choices and underscoring the study’s contribution to the field. This careful articulation ensures that the research is perceived as a well-thought-out endeavor, grounded in a strategic approach to inquiry.

The scope and delimitations of a study are foundational elements that guide the research process, setting clear boundaries and focusing efforts. By defining these aspects clearly, researchers can provide a clear roadmap for their investigation, ensuring that their work is both manageable and relevant. By consciously deciding what to exclude from the study, researchers can intensify their focus on the chosen subject, ensuring that the research efforts are concentrated where they are most needed and can be most effective. These self-imposed boundaries are critical for maintaining the study’s coherence and depth. This clarity not only aids in conducting the research but also in effectively communicating its implications, limits, and outcomes.

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The limitations of the study are those characteristics of design or methodology that impacted or influenced the interpretation of the findings from your research. Study limitations are the constraints placed on the ability to generalize from the results, to further describe applications to practice, and/or related to the utility of findings that are the result of the ways in which you initially chose to design the study or the method used to establish internal and external validity or the result of unanticipated challenges that emerged during the study.

Price, James H. and Judy Murnan. “Research Limitations and the Necessity of Reporting Them.” American Journal of Health Education 35 (2004): 66-67; Theofanidis, Dimitrios and Antigoni Fountouki. "Limitations and Delimitations in the Research Process." Perioperative Nursing 7 (September-December 2018): 155-163. .

Importance of...

Always acknowledge a study's limitations. It is far better that you identify and acknowledge your study’s limitations than to have them pointed out by your professor and have your grade lowered because you appeared to have ignored them or didn't realize they existed.

Keep in mind that acknowledgment of a study's limitations is an opportunity to make suggestions for further research. If you do connect your study's limitations to suggestions for further research, be sure to explain the ways in which these unanswered questions may become more focused because of your study.

Acknowledgment of a study's limitations also provides you with opportunities to demonstrate that you have thought critically about the research problem, understood the relevant literature published about it, and correctly assessed the methods chosen for studying the problem. A key objective of the research process is not only discovering new knowledge but also to confront assumptions and explore what we don't know.

Claiming limitations is a subjective process because you must evaluate the impact of those limitations . Don't just list key weaknesses and the magnitude of a study's limitations. To do so diminishes the validity of your research because it leaves the reader wondering whether, or in what ways, limitation(s) in your study may have impacted the results and conclusions. Limitations require a critical, overall appraisal and interpretation of their impact. You should answer the question: do these problems with errors, methods, validity, etc. eventually matter and, if so, to what extent?

Price, James H. and Judy Murnan. “Research Limitations and the Necessity of Reporting Them.” American Journal of Health Education 35 (2004): 66-67; Structure: How to Structure the Research Limitations Section of Your Dissertation. Dissertations and Theses: An Online Textbook. Laerd.com.

Descriptions of Possible Limitations

All studies have limitations . However, it is important that you restrict your discussion to limitations related to the research problem under investigation. For example, if a meta-analysis of existing literature is not a stated purpose of your research, it should not be discussed as a limitation. Do not apologize for not addressing issues that you did not promise to investigate in the introduction of your paper.

Here are examples of limitations related to methodology and the research process you may need to describe and discuss how they possibly impacted your results. Note that descriptions of limitations should be stated in the past tense because they were discovered after you completed your research.

Possible Methodological Limitations

• Sample size -- the number of the units of analysis you use in your study is dictated by the type of research problem you are investigating. Note that, if your sample size is too small, it will be difficult to find significant relationships from the data, as statistical tests normally require a larger sample size to ensure a representative distribution of the population and to be considered representative of groups of people to whom results will be generalized or transferred. Note that sample size is generally less relevant in qualitative research if explained in the context of the research problem.
• Lack of available and/or reliable data -- a lack of data or of reliable data will likely require you to limit the scope of your analysis, the size of your sample, or it can be a significant obstacle in finding a trend and a meaningful relationship. You need to not only describe these limitations but provide cogent reasons why you believe data is missing or is unreliable. However, don’t just throw up your hands in frustration; use this as an opportunity to describe a need for future research based on designing a different method for gathering data.
• Lack of prior research studies on the topic -- citing prior research studies forms the basis of your literature review and helps lay a foundation for understanding the research problem you are investigating. Depending on the currency or scope of your research topic, there may be little, if any, prior research on your topic. Before assuming this to be true, though, consult with a librarian! In cases when a librarian has confirmed that there is little or no prior research, you may be required to develop an entirely new research typology [for example, using an exploratory rather than an explanatory research design ]. Note again that discovering a limitation can serve as an important opportunity to identify new gaps in the literature and to describe the need for further research.
• Measure used to collect the data -- sometimes it is the case that, after completing your interpretation of the findings, you discover that the way in which you gathered data inhibited your ability to conduct a thorough analysis of the results. For example, you regret not including a specific question in a survey that, in retrospect, could have helped address a particular issue that emerged later in the study. Acknowledge the deficiency by stating a need for future researchers to revise the specific method for gathering data.
• Self-reported data -- whether you are relying on pre-existing data or you are conducting a qualitative research study and gathering the data yourself, self-reported data is limited by the fact that it rarely can be independently verified. In other words, you have to the accuracy of what people say, whether in interviews, focus groups, or on questionnaires, at face value. However, self-reported data can contain several potential sources of bias that you should be alert to and note as limitations. These biases become apparent if they are incongruent with data from other sources. These are: (1) selective memory [remembering or not remembering experiences or events that occurred at some point in the past]; (2) telescoping [recalling events that occurred at one time as if they occurred at another time]; (3) attribution [the act of attributing positive events and outcomes to one's own agency, but attributing negative events and outcomes to external forces]; and, (4) exaggeration [the act of representing outcomes or embellishing events as more significant than is actually suggested from other data].

Possible Limitations of the Researcher

• Access -- if your study depends on having access to people, organizations, data, or documents and, for whatever reason, access is denied or limited in some way, the reasons for this needs to be described. Also, include an explanation why being denied or limited access did not prevent you from following through on your study.
• Longitudinal effects -- unlike your professor, who can literally devote years [even a lifetime] to studying a single topic, the time available to investigate a research problem and to measure change or stability over time is constrained by the due date of your assignment. Be sure to choose a research problem that does not require an excessive amount of time to complete the literature review, apply the methodology, and gather and interpret the results. If you're unsure whether you can complete your research within the confines of the assignment's due date, talk to your professor.
• Cultural and other type of bias -- we all have biases, whether we are conscience of them or not. Bias is when a person, place, event, or thing is viewed or shown in a consistently inaccurate way. Bias is usually negative, though one can have a positive bias as well, especially if that bias reflects your reliance on research that only support your hypothesis. When proof-reading your paper, be especially critical in reviewing how you have stated a problem, selected the data to be studied, what may have been omitted, the manner in which you have ordered events, people, or places, how you have chosen to represent a person, place, or thing, to name a phenomenon, or to use possible words with a positive or negative connotation. NOTE :   If you detect bias in prior research, it must be acknowledged and you should explain what measures were taken to avoid perpetuating that bias. For example, if a previous study only used boys to examine how music education supports effective math skills, describe how your research expands the study to include girls.
• Fluency in a language -- if your research focuses , for example, on measuring the perceived value of after-school tutoring among Mexican-American ESL [English as a Second Language] students and you are not fluent in Spanish, you are limited in being able to read and interpret Spanish language research studies on the topic or to speak with these students in their primary language. This deficiency should be acknowledged.

Aguinis, Hermam and Jeffrey R. Edwards. “Methodological Wishes for the Next Decade and How to Make Wishes Come True.” Journal of Management Studies 51 (January 2014): 143-174; Brutus, Stéphane et al. "Self-Reported Limitations and Future Directions in Scholarly Reports: Analysis and Recommendations." Journal of Management 39 (January 2013): 48-75; Senunyeme, Emmanuel K. Business Research Methods. Powerpoint Presentation. Regent University of Science and Technology; ter Riet, Gerben et al. “All That Glitters Isn't Gold: A Survey on Acknowledgment of Limitations in Biomedical Studies.” PLOS One 8 (November 2013): 1-6.

Structure and Writing Style

Information about the limitations of your study are generally placed either at the beginning of the discussion section of your paper so the reader knows and understands the limitations before reading the rest of your analysis of the findings, or, the limitations are outlined at the conclusion of the discussion section as an acknowledgement of the need for further study. Statements about a study's limitations should not be buried in the body [middle] of the discussion section unless a limitation is specific to something covered in that part of the paper. If this is the case, though, the limitation should be reiterated at the conclusion of the section.

If you determine that your study is seriously flawed due to important limitations , such as, an inability to acquire critical data, consider reframing it as an exploratory study intended to lay the groundwork for a more complete research study in the future. Be sure, though, to specifically explain the ways that these flaws can be successfully overcome in a new study.

But, do not use this as an excuse for not developing a thorough research paper! Review the tab in this guide for developing a research topic . If serious limitations exist, it generally indicates a likelihood that your research problem is too narrowly defined or that the issue or event under study is too recent and, thus, very little research has been written about it. If serious limitations do emerge, consult with your professor about possible ways to overcome them or how to revise your study.

When discussing the limitations of your research, be sure to:

• Describe each limitation in detailed but concise terms;
• Explain why each limitation exists;
• Provide the reasons why each limitation could not be overcome using the method(s) chosen to acquire or gather the data [cite to other studies that had similar problems when possible];
• Assess the impact of each limitation in relation to the overall findings and conclusions of your study; and,
• If appropriate, describe how these limitations could point to the need for further research.

Remember that the method you chose may be the source of a significant limitation that has emerged during your interpretation of the results [for example, you didn't interview a group of people that you later wish you had]. If this is the case, don't panic. Acknowledge it, and explain how applying a different or more robust methodology might address the research problem more effectively in a future study. A underlying goal of scholarly research is not only to show what works, but to demonstrate what doesn't work or what needs further clarification.

Aguinis, Hermam and Jeffrey R. Edwards. “Methodological Wishes for the Next Decade and How to Make Wishes Come True.” Journal of Management Studies 51 (January 2014): 143-174; Brutus, Stéphane et al. "Self-Reported Limitations and Future Directions in Scholarly Reports: Analysis and Recommendations." Journal of Management 39 (January 2013): 48-75; Ioannidis, John P.A. "Limitations are not Properly Acknowledged in the Scientific Literature." Journal of Clinical Epidemiology 60 (2007): 324-329; Pasek, Josh. Writing the Empirical Social Science Research Paper: A Guide for the Perplexed. January 24, 2012. Academia.edu; Structure: How to Structure the Research Limitations Section of Your Dissertation. Dissertations and Theses: An Online Textbook. Laerd.com; What Is an Academic Paper? Institute for Writing Rhetoric. Dartmouth College; Writing the Experimental Report: Methods, Results, and Discussion. The Writing Lab and The OWL. Purdue University.

Writing Tip

Don't Inflate the Importance of Your Findings!

After all the hard work and long hours devoted to writing your research paper, it is easy to get carried away with attributing unwarranted importance to what you’ve done. We all want our academic work to be viewed as excellent and worthy of a good grade, but it is important that you understand and openly acknowledge the limitations of your study. Inflating the importance of your study's findings could be perceived by your readers as an attempt hide its flaws or encourage a biased interpretation of the results. A small measure of humility goes a long way!

Another Writing Tip

Negative Results are Not a Limitation!

Negative evidence refers to findings that unexpectedly challenge rather than support your hypothesis. If you didn't get the results you anticipated, it may mean your hypothesis was incorrect and needs to be reformulated. Or, perhaps you have stumbled onto something unexpected that warrants further study. Moreover, the absence of an effect may be very telling in many situations, particularly in experimental research designs. In any case, your results may very well be of importance to others even though they did not support your hypothesis. Do not fall into the trap of thinking that results contrary to what you expected is a limitation to your study. If you carried out the research well, they are simply your results and only require additional interpretation.

Lewis, George H. and Jonathan F. Lewis. “The Dog in the Night-Time: Negative Evidence in Social Research.” The British Journal of Sociology 31 (December 1980): 544-558.

Yet Another Writing Tip

Sample Size Limitations in Qualitative Research

Sample sizes are typically smaller in qualitative research because, as the study goes on, acquiring more data does not necessarily lead to more information. This is because one occurrence of a piece of data, or a code, is all that is necessary to ensure that it becomes part of the analysis framework. However, it remains true that sample sizes that are too small cannot adequately support claims of having achieved valid conclusions and sample sizes that are too large do not permit the deep, naturalistic, and inductive analysis that defines qualitative inquiry. Determining adequate sample size in qualitative research is ultimately a matter of judgment and experience in evaluating the quality of the information collected against the uses to which it will be applied and the particular research method and purposeful sampling strategy employed. If the sample size is found to be a limitation, it may reflect your judgment about the methodological technique chosen [e.g., single life history study versus focus group interviews] rather than the number of respondents used.

Boddy, Clive Roland. "Sample Size for Qualitative Research." Qualitative Market Research: An International Journal 19 (2016): 426-432; Huberman, A. Michael and Matthew B. Miles. "Data Management and Analysis Methods." In Handbook of Qualitative Research . Norman K. Denzin and Yvonna S. Lincoln, eds. (Thousand Oaks, CA: Sage, 1994), pp. 428-444; Blaikie, Norman. "Confounding Issues Related to Determining Sample Size in Qualitative Research." International Journal of Social Research Methodology 21 (2018): 635-641; Oppong, Steward Harrison. "The Problem of Sampling in qualitative Research." Asian Journal of Management Sciences and Education 2 (2013): 202-210.

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Diving Deeper into Limitations and Delimitations

If you are working on a thesis, dissertation, or other formal research project, chances are your advisor or committee will ask you to address the delimitations of your study. When faced with this request, many students respond with a puzzled look and then go on to address what are actually the study’s limitations.

In a previous article , we covered what goes into the limitations, delimitations, and assumptions sections of your thesis or dissertation. Here, we will dive a bit deeper into the differences between limitations and delimitations and provide some helpful tips for addressing them in your research project—whether you are working on a quantitative or qualitative study.

Acknowledging Weaknesses vs. Defining Boundaries

These concepts are easy to get confused because both limitations and delimitations restrict (or limit) the questions you’ll be able to answer with your study, most notably in terms of generalizability.

However, the biggest difference between limitations and delimitations is the degree of control you have over them—that is, how much they are based in conscious, intentional choices you made in designing your study.

Limitations occur in all types of research and are, for the most part, outside the researcher’s control (given practical constraints, such as time, funding, and access to populations of interest). They are threats to the study’s internal or external validity.

Limitations may include things such as participant drop-out, a sample that isn’t entirely representative of the desired population, violations to the assumptions of parametric analysis (e.g., normality, homogeneity of variance), the limits of self-report, or the absence of reliability and validity data for some of your survey measures.

Limitations can get in the way of your being able to answer certain questions or draw certain types of inferences from your findings. Therefore, it’s important to acknowledge them upfront and make note of how they restrict the conclusions you’ll be able to draw from your study. Frequently, limitations can get in the way of our ability to generalize our findings to the larger populations or to draw causal conclusions, so be sure to consider these issues when you’re thinking about the potential limitations of your study.

Delimitations are also factors that can restrict the questions you can answer or the inferences you can draw from your findings. However, they are based on intentional choices you make a priori (i.e., as you’re designing the study) about where you’re going to draw the boundaries of your project. In other words, they define the project’s scope.

Like limitations, delimitations are a part of every research project, and this is not a bad thing. In fact, it’s very important! You can’t study everything at once. If you try to do so, your project is bound to get huge and unwieldy, and it will become a lot more difficult to interpret your results or come to meaningful conclusions with so many moving parts. You have to draw the line somewhere, and the delimitations are where you choose to draw these lines.

One of the clearest examples of a delimitation that applies to almost every research project is participant exclusion criteria. In conducting either a quantitative or a qualitative study, you will have to define your population of interest. Defining this population of interest means that you will need to articulate the boundaries of that population (i.e., who is not included). Those boundaries are delimitations.

For example, if you’re interested in understanding the experiences of elementary school teachers who have been implementing a new curriculum into their classrooms, you probably won’t be interviewing or sending a survey to any of the following people: non-teachers, high-school teachers, college professors, principals, parents of elementary school children, or the children themselves. Furthermore, you probably won’t be talking to elementary school teachers who have not yet had the experience of implementing the curriculum in question. You would probably only choose to gather data from elementary school teachers who have had this experience because that is who you’re interested in for the purposes of your study. Perhaps you’ll narrow your focus even more to elementary school teachers in a particular school district who have been teaching for a particular length of time. The possibilities can go on. These are choices you will need to make, both for practical reasons (i.e., the population you have access to) and for the questions you are trying to answer.

Of course, for this particular example, this does not mean that it wouldn’t be interesting to also know what principals think about the new curriculum. Or parents. Or elementary school children. It just means that, for the purposes of your project and your research questions, you’re interested in the experience of the teachers, so you’re excluding anyone who does not meet those criteria. Having delimitations to your population of interest also means that you won’t be able to answer any questions about the experiences of those other populations; this is ok because those populations are outside of the scope of your project . As interesting as their experiences might be, you can save these questions for another study. That is the part of the beauty of research: there will always be more studies to do, more questions to ask. You don’t have to (and can’t) do it all in one project.

Continuing with the previous example, for instance, let’s suppose that the problem you are most interested in addressing is the fact that we know relatively little about elementary school teachers’ experiences of implementing a new curriculum. Perhaps you believe that knowing more about teachers’ experiences could inform their training or help administrators know more about how to support their teachers. If the identified problem is our lack of knowledge about teachers’ experiences, and your research questions focus on better understanding these experiences, that means that you are choosing not to focus on other problems or questions, even those that may seem closely related. For instance, you are not asking how effective the new curriculum is in improving student test scores or graduation rates. You might think that would be a very interesting question, but it will have to wait for another study. In narrowing the focus of your research questions, you limit your ability to answer other questions, and again, that’s ok. These other questions may be interesting and important, but, again, they are beyond the scope of your project .

Common Examples of Limitations

While each study will have its own unique set of limitations, some limitations are more common in quantitative research, and others are more common in qualitative research.

In quantitative research, common limitations include the following:

– Participant dropout

– Small sample size, low power

– Non-representative sample

– Violations of statistical assumptions

– Non-experimental design, lack of manipulation of variables, lack of controls

– Potential confounding variables

– Measures with low (or unknown) reliability or validity

– Limits of an instrument to measure the construct of interest

– Data collection methods (e.g., self-report)

– Anything else that might limit the study’s internal or external validity

In qualitative research, common limitations include the following:

– Lack of generalizability of findings (not the goal of qualitative research, but still worth mentioning as a limitation)

– Inability to draw causal conclusions (again, not the goal of qualitative research, but still worth mentioning)

– Researcher bias/subjectivity (especially if there is only one coder)

– Limitations in participants’ ability/willingness to share or describe their experiences

– Any factors that might limit the rigor of data collection or analysis procedures

Common Examples of Delimitations

As noted above, the two most common sources of delimitations in both quantitative and qualitative research include the following:

– Inclusion/exclusion criteria (or how you define your population of interest)

– Research questions or problems you’ve chosen to examine

Several other common sources of delimitations include the following:

– Theoretical framework or perspective adopted

– Methodological framework or paradigm chosen (e.g., quantitative, qualitative, or mixed-methods)

– In quantitative research, the variables you’ve chosen to measure or manipulate (as opposed to others)

Whether you’re conducting a quantitative or qualitative study, you will (hopefully!) have chosen your research design because it is well suited to the questions you’re hoping to answer. Because these questions define the boundaries or scope of your project and thus point to its delimitations, your research design itself will also be related to these delimitations.

Questions to Ask Yourself

As you are considering the limitations and delimitations of your project, it can be helpful to ask yourself a few different questions.

Questions to help point out your study’s limitations :

1. If I had an unlimited budget, unlimited amounts of time, access to all possible populations, and the ability to manipulate as many variables as I wanted, how would I design my study differently to be better able to answer the questions I want to answer? (The ways in which your study falls short of this will point to its limitations.)

2. Are there design issues that get in the way of my being able to draw causal conclusions?

3. Are there sampling issues that get in the way of my being able to generalize my findings?

4. Are there issues related to the measures I’m using or the methods I’m using to collect data? Do I have concerns about participants telling the truth or being able to provide accurate responses to my questions?

5. Are there any other factors that might limit my study’s internal or external validity?

Questions that help point out your study’s delimitations :

1. What are my exclusion criteria? Who did I not include in my study, and why did I make this choice?

2. What questions did I choose not to address in my study? (Of course, the possibilities are endless here, but consider related questions that you chose not to address.)

3. In what ways did I narrow the scope of my study in order to hone in on a particular issue or question?

4. What other methodologies did I not use that might have allowed me to answer slightly different questions about the same topic?

How to Write About Limitations and Delimitations

Remember, having limitations and delimitations is not a bad thing. They’re present in even the most rigorous research. The important thing is to be aware of them and to acknowledge how they may impact your findings or the conclusions you can draw.

In fact, writing about them and acknowledging them gives you an opportunity to demonstrate that you can think critically about these aspects of your study and how they impact your findings, even if they were out of your control.

Keep in mind that your study’s limitations will likely point to important directions for future research. Therefore, when you’re getting ready to write about your recommendations for future research in your discussion, remember to refer back to your limitations section!

As you write about your delimitations in particular, remember that they are not weaknesses, and you don’t have to apologize for them. Good, strong research projects have clear boundaries. Also, keep in mind that you are the researcher and you can choose whatever delimitations you want for your study. You’re in control of the delimitations. You just have to be prepared—both in your discussion section and in your dissertation defense itself—to justify the choices you make and acknowledge how these choices impact your findings.

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Exploring Scope and Delimitation in Academic Research

Academic research is a meticulous process that requires precise planning and clear boundaries. Two pivotal components in this process are the scope and delimitations of the study. The definitions and establishment of these parameters are instrumental in ensuring that the research is effective, manageable, and yields relevant results.

The "scope" of a research project refers to the areas that the study will cover. It is the breadth and depth of the investigation. It defines the subject matter, the geographical location, the time frame, and the issues that the study will explore. Essentially, the scope delineates what the researcher aims to cover in the study.

On the other hand, "delimitations" are the boundaries or limitations set by the researcher. They define what the study will not include. Delimitations could involve the choice of research methodology , the selection of respondents, the duration of the study, and more. They help in confining the study to a manageable size while excluding peripheral elements.

Understanding and correctly implementing scope and delimitations are vital to ensuring your research is well-defined and focused, facilitating higher accuracy and relevancy in your findings.

Importance of scope in research

"Scope" in research refers to the comprehensive extent of study—it outlines the parameters of what will be explored and addressed. It defines the topic of the research , the geographical region under study, the timeframe considered, and the issues that the study will address. The scope of a research project is vital because it determines the depth and breadth of your investigation.

Defining the scope of research is a fundamental step in the research process for several reasons. First, it provides a roadmap for the study, giving the researcher clear guidelines about what to include and exclude. Without a well-defined scope, research can become unmanageably vast or lose its focus.

Second, the scope ensures the research's relevance and applicability. It helps the researcher maintain a tight focus on the study's central question , ensuring that all aspects of the research contribute to answering this question. This focus aids in avoiding irrelevant diversions that could dilute the final conclusions.

Finally, a well-defined scope can help ensure the efficient use of resources. Research involves considerable time, effort, and often financial resources. By providing clear boundaries, the scope ensures these resources are utilized effectively without wasted effort on peripheral issues.

Suppose a research study is looking at the impacts of social media usage on mental health. If the scope is too broad—like examining all social media platforms' effects on all demographic groups worldwide—then the research can quickly become unwieldy and hard to manage. It would involve vast amounts of data, requiring considerable time, resources, and computational power to analyze effectively.

However, if the scope is narrowed down—such as investigating the impact of Instagram usage on the mental health of teenagers in a specific city over the past five years—the research becomes far more manageable. This specific focus allows for a more in-depth analysis and likely will provide more meaningful, actionable results. This example illustrates the importance of appropriately defining the scope of research for its successful execution.

Determining the scope of your research

Setting the scope of your research project is a critical and delicate task. Below are steps, tips, and common mistakes to avoid when determining the scope of your research:

Steps to define the scope

• Identify Your Topic: The first step involves identifying and understanding your research topic. This knowledge will serve as a basis for determining the breadth and depth of your study.
• Define Your Research Questions: The research questions are the heart of your study. They will help you determine the specific areas your research should cover.
• Establish Boundaries: Clearly establish the geographical, temporal, and topical boundaries of your research. These boundaries will guide the range of your study.
• Choose Your Methodology: Decide on the research methods you will use as these will directly impact the scope of your study.

Tips for a manageable scope

• Stay Focused: Stay concentrated on your research questions. Do not stray into areas that aren't directly relevant.
• Be Realistic: Consider the resources (time, money, manpower) available. Ensure your scope is feasible given these resources.
• Seek Guidance: Consult with your academic advisor or peers for feedback on your proposed scope.

Common mistakes to avoid

• Overly Broad Scope: Avoid setting an overly broad scope which could result in an unmanageable and unfocused study.
• Too Narrow Scope: Conversely, a scope that is too narrow may miss important aspects of the research topic.
• Ignoring Resources: Not taking into account available resources when setting the scope can lead to a project that is impossible to complete.

Defining the scope of your research is a delicate balance, requiring careful consideration of your research questions, resources, and the depth and breadth of investigation needed to answer these questions effectively.

Importance of delimitations in research

In the context of academic research, "delimitations" refers to the choices made by the researcher which define the boundaries of the study. These are the variables that lead the researcher to narrow the scope of the study from its potential vastness to a manageable size.

Delimitations might include the geographic area where the study is confined, the participants involved in the study, the methodology used, the time period considered, or the specific incidents or aspects the study will focus on. Essentially, delimitations are the self-imposed limitations on the scope of the study.

Defining the delimitations of a research project is crucial for several reasons. Firstly, they establish the context or setting in which the study occurs. This, in turn, allows for the work to be reproduced in a similar context for verification or refutation in future studies.

Secondly, delimitations provide a way to narrow the scope of the research to a manageable size, thus avoiding the pitfall of an overly ambitious project. They help researchers to stay focused on the main research questions and prevent diversion into irrelevant aspects.

Finally, clearly defined delimitations enhance the credibility of the research. They offer transparency about the research design and methodology, which adds to the validity of the results.

For instance, in a research study examining the impact of technology on student achievement in a certain district, examples of delimitations might include focusing only on public schools, considering only high school students, and confining the study to a particular school year. These choices help to focus the research and ensure its manageability. Therefore, delimitations play a pivotal role in structuring and guiding an effective and efficient research study.

Setting delimitations for your research

Establishing appropriate delimitations for your research project is an important part of research design. Here are some steps, guidelines, and common mistakes to consider when setting your research delimitations:

Steps to establish delimitations

• Identify the boundaries: Begin by deciding the geographical region, time period, and subject matter your research will cover.
• Determine Your Research Population: Identify the specific population your study will focus on. This could be based on age, profession, geographical location, etc.
• Choose Your Research Methods: Decide the specific methods you will use to collect and analyze data, as these decisions will also set limitations on your study.

Guidelines for choosing delimitations

• Align with Your Research Objectives: The delimitations should be in line with your research questions and objectives. They should help focus your study without detracting from its goals.
• Be Practical: Consider the resources available, including time, funds, and access to data. Your delimitations should be feasible given these constraints.
• Seek Input: Consult with your research advisor or peers. Their feedback can help ensure your delimitations are appropriate and well thought out.

Common errors to avoid:

• Unrealistic Delimitations: Be wary of setting delimitations that are too stringent or ambitious to be feasible given your resources and timeframe.
• Undefined Delimitations: Avoid leaving your delimitations vague or undefined. This can lead to scope creep, where your project expands beyond its initial plan, making it unmanageable.
• Ignoring Delimitations: Once set, stick to your delimitations. Deviating from them can lead to a loss of focus and can compromise the integrity of your results.

Setting delimitations is a crucial step in research planning. Properly defined delimitations can make your research project more manageable, maintain your focus, and ensure the effective use of your resources.

The interplay between scope and delimitations

The relationship between scope and delimitations in academic research is a dynamic and interdependent one. Each aspect serves to shape and refine the other, ultimately leading to a focused, feasible, and effective research design.

The scope of a research project describes the breadth and depth of the investigation—what it aims to cover and how far it intends to delve into the subject matter. The delimitations, on the other hand, identify the boundaries and constraints of the study—what it will not cover.

As such, the scope and delimitations of a research study are intimately connected. When the scope of a study is broad, the delimitations must be carefully considered to ensure the project remains manageable and focused. Conversely, when the scope is narrow, the delimitations might be less constraining, but they still play a critical role in defining the specificity of the research.

Balancing the scope and delimitations is crucial for an efficient research design. Too broad a scope without carefully defined delimitations can lead to a study that is unwieldy and lacks depth. On the other hand, a very narrow scope with overly rigid delimitations might result in a study that overlooks important aspects of the research topic.

Thus, researchers must strive to maintain a balance—establishing a scope that is wide enough to fully explore the research topic, but also setting appropriate delimitations to ensure the study remains feasible and focused. In doing so, the research will be well-structured and yield meaningful, relevant findings.

Role of scope and delimitations in research validity

Scope and delimitations are fundamental aspects of research design that directly influence the validity, reliability, and replicability of a study.

Research validity refers to the degree to which a study accurately reflects or measures the concept that the researcher intends to investigate. A well-defined scope is critical to research validity because it clearly delineates what the study will cover. This clear definition ensures that the research focuses on relevant aspects of the topic and that the findings accurately reflect the concept under investigation.

Similarly, carefully thought-out delimitations contribute to research validity by identifying what the study will not cover. This clarity helps to prevent the study from straying into irrelevant areas, ensuring that the research stays focused and relevant.

In addition to contributing to research validity, scope and delimitations also influence the reliability and replicability of a study. Reliability refers to the consistency of a study's results, while replicability refers to the ability of other researchers to repeat the study and obtain similar results.

A clearly defined scope makes a study more reliable by providing a detailed outline of the areas covered by the research. This clarity makes it more likely that the study will produce consistent results. Moreover, clearly defined delimitations enhance the replicability of a study by providing explicit boundaries for the research, which makes it easier for other researchers to repeat the study in a similar context.

In summary, a well-defined scope and carefully thought-out delimitations contribute significantly to the validity, reliability, and replicability of academic research. They ensure that the research is focused, that the findings are relevant and accurate, and that the study can be reliably repeated by other researchers.

Examples of scope and delimitation in well-known research

• The Milgram Experiment: Stanley Milgram's famous psychology experiment sought to understand obedience to authority figures. The scope of this study was clearly defined—it focused on how far individuals would go in obeying an instruction if it involved harming another person. However, delimitations were set to ensure manageability. Participants were delimited to male individuals, and the experiment was confined to a controlled laboratory setting. These delimitations allowed Milgram to manage the research effectively while maintaining the depth of his study on human behavior.
• The Framingham Heart Study: This ongoing cardiovascular study began in 1948 and is aimed at identifying common factors that contribute to cardiovascular disease. The scope of the research is broad, covering many aspects of lifestyle, medical history, and physical characteristics. However, the study set clear delimitations: it initially only involved adult residents of Framingham, Massachusetts. This geographical delimitation made this broad-scope study manageable and eventually yielded influential results that shaped our understanding of heart disease.
• The Marshmallow Test: This well-known study by Walter Mischel explored delayed gratification in children. The scope was clearly defined: the study aimed to understand the ability of children to delay gratification and how it related to future success. The delimitations of the study included the age of the participants (preschool children), the setting (a controlled experiment with a treat), and the measure of future success (academic achievement, ability to cope with stress, etc.). These delimitations helped keep the study focused and manageable.

In all these examples, the researchers set a clear scope to outline the focus of their studies and used delimitations to restrict the boundaries. This balance between scope and delimitation was key in conducting successful and influential research.

In academic research, defining the scope and delimitations is a pivotal step in designing a robust and effective study. The scope outlines the breadth and depth of the investigation, offering a clear direction for the research. Meanwhile, delimitations set the boundaries of the study, ensuring that the research remains focused and manageable. Together, they play a crucial role in enhancing the validity, reliability, and replicability of a study.

Understanding the interplay between scope and delimitations is key to conducting efficient research. A well-defined scope paired with thoughtfully set delimitations contribute to a study's feasibility and its potential to yield meaningful and applicable results. Mistakes in setting the scope and delimitations can lead to unwieldy, unfocused research or a study that overlooks important aspects of a research question.

Reviewing famous studies, like the Milgram Experiment, the Framingham Heart Study, and the Marshmallow Test, we observe how a balanced approach to setting scope and delimitations can result in influential and valuable findings. Therefore, researchers should give careful thought to defining the scope and delimitations of their studies, keeping in mind their research questions, available resources, and the need for balance between breadth and focus. By doing so, they pave the way for successful and impactful research outcomes.

Header image by Kübra Arslaner .

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How to Write Limitations of the Study (with examples)

This blog emphasizes the importance of recognizing and effectively writing about limitations in research. It discusses the types of limitations, their significance, and provides guidelines for writing about them, highlighting their role in advancing scholarly research.

Updated on August 24, 2023

No matter how well thought out, every research endeavor encounters challenges. There is simply no way to predict all possible variances throughout the process.

These uncharted boundaries and abrupt constraints are known as limitations in research . Identifying and acknowledging limitations is crucial for conducting rigorous studies. Limitations provide context and shed light on gaps in the prevailing inquiry and literature.

This article explores the importance of recognizing limitations and discusses how to write them effectively. By interpreting limitations in research and considering prevalent examples, we aim to reframe the perception from shameful mistakes to respectable revelations.

What are limitations in research?

In the clearest terms, research limitations are the practical or theoretical shortcomings of a study that are often outside of the researcher’s control . While these weaknesses limit the generalizability of a study’s conclusions, they also present a foundation for future research.

Sometimes limitations arise from tangible circumstances like time and funding constraints, or equipment and participant availability. Other times the rationale is more obscure and buried within the research design. Common types of limitations and their ramifications include:

• Theoretical: limits the scope, depth, or applicability of a study.
• Methodological: limits the quality, quantity, or diversity of the data.
• Empirical: limits the representativeness, validity, or reliability of the data.
• Analytical: limits the accuracy, completeness, or significance of the findings.
• Ethical: limits the access, consent, or confidentiality of the data.

Regardless of how, when, or why they arise, limitations are a natural part of the research process and should never be ignored . Like all other aspects, they are vital in their own purpose.

Why is identifying limitations important?

Whether to seek acceptance or avoid struggle, humans often instinctively hide flaws and mistakes. Merging this thought process into research by attempting to hide limitations, however, is a bad idea. It has the potential to negate the validity of outcomes and damage the reputation of scholars.

By identifying and addressing limitations throughout a project, researchers strengthen their arguments and curtail the chance of peer censure based on overlooked mistakes. Pointing out these flaws shows an understanding of variable limits and a scrupulous research process.

Showing awareness of and taking responsibility for a project’s boundaries and challenges validates the integrity and transparency of a researcher. It further demonstrates the researchers understand the applicable literature and have thoroughly evaluated their chosen research methods.

Presenting limitations also benefits the readers by providing context for research findings. It guides them to interpret the project’s conclusions only within the scope of very specific conditions. By allowing for an appropriate generalization of the findings that is accurately confined by research boundaries and is not too broad, limitations boost a study’s credibility .

Limitations are true assets to the research process. They highlight opportunities for future research. When researchers identify the limitations of their particular approach to a study question, they enable precise transferability and improve chances for reproducibility. 

Simply stating a project’s limitations is not adequate for spurring further research, though. To spark the interest of other researchers, these acknowledgements must come with thorough explanations regarding how the limitations affected the current study and how they can potentially be overcome with amended methods.

How to write limitations

Typically, the information about a study’s limitations is situated either at the beginning of the discussion section to provide context for readers or at the conclusion of the discussion section to acknowledge the need for further research. However, it varies depending upon the target journal or publication guidelines. 

Don’t hide your limitations

It is also important to not bury a limitation in the body of the paper unless it has a unique connection to a topic in that section. If so, it needs to be reiterated with the other limitations or at the conclusion of the discussion section. Wherever it is included in the manuscript, ensure that the limitations section is prominently positioned and clearly introduced.

While maintaining transparency by disclosing limitations means taking a comprehensive approach, it is not necessary to discuss everything that could have potentially gone wrong during the research study. If there is no commitment to investigation in the introduction, it is unnecessary to consider the issue a limitation to the research. Wholly consider the term ‘limitations’ and ask, “Did it significantly change or limit the possible outcomes?” Then, qualify the occurrence as either a limitation to include in the current manuscript or as an idea to note for other projects. 

Writing limitations

Once the limitations are concretely identified and it is decided where they will be included in the paper, researchers are ready for the writing task. Including only what is pertinent, keeping explanations detailed but concise, and employing the following guidelines is key for crafting valuable limitations:

1) Identify and describe the limitations : Clearly introduce the limitation by classifying its form and specifying its origin. For example:

• An unintentional bias encountered during data collection
• An intentional use of unplanned post-hoc data analysis

2) Explain the implications : Describe how the limitation potentially influences the study’s findings and how the validity and generalizability are subsequently impacted. Provide examples and evidence to support claims of the limitations’ effects without making excuses or exaggerating their impact. Overall, be transparent and objective in presenting the limitations, without undermining the significance of the research. 

3) Provide alternative approaches for future studies : Offer specific suggestions for potential improvements or avenues for further investigation. Demonstrate a proactive approach by encouraging future research that addresses the identified gaps and, therefore, expands the knowledge base.

Whether presenting limitations as an individual section within the manuscript or as a subtopic in the discussion area, authors should use clear headings and straightforward language to facilitate readability. There is no need to complicate limitations with jargon, computations, or complex datasets.

Examples of common limitations

Limitations are generally grouped into two categories , methodology and research process .

Methodology limitations

Methodology may include limitations due to:

• Sample size
• Lack of available or reliable data
• Lack of prior research studies on the topic
• Measure used to collect the data
• Self-reported data

The researcher is addressing how the large sample size requires a reassessment of the measures used to collect and analyze the data.

Research process limitations

Limitations during the research process may arise from:

• Access to information
• Longitudinal effects
• Cultural and other biases
• Language fluency
• Time constraints

The author is pointing out that the model’s estimates are based on potentially biased observational studies.

Final thoughts

Successfully proving theories and touting great achievements are only two very narrow goals of scholarly research. The true passion and greatest efforts of researchers comes more in the form of confronting assumptions and exploring the obscure.

In many ways, recognizing and sharing the limitations of a research study both allows for and encourages this type of discovery that continuously pushes research forward. By using limitations to provide a transparent account of the project's boundaries and to contextualize the findings, researchers pave the way for even more robust and impactful research in the future.

Charla Viera, MS

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• Perspect Med Educ
• v.8(4); 2019 Aug

Limited by our limitations

Paula t. ross.

Medical School, University of Michigan, Ann Arbor, MI USA

Nikki L. Bibler Zaidi

Study limitations represent weaknesses within a research design that may influence outcomes and conclusions of the research. Researchers have an obligation to the academic community to present complete and honest limitations of a presented study. Too often, authors use generic descriptions to describe study limitations. Including redundant or irrelevant limitations is an ineffective use of the already limited word count. A meaningful presentation of study limitations should describe the potential limitation, explain the implication of the limitation, provide possible alternative approaches, and describe steps taken to mitigate the limitation. This includes placing research findings within their proper context to ensure readers do not overemphasize or minimize findings. A more complete presentation will enrich the readers’ understanding of the study’s limitations and support future investigation.

Introduction

Regardless of the format scholarship assumes, from qualitative research to clinical trials, all studies have limitations. Limitations represent weaknesses within the study that may influence outcomes and conclusions of the research. The goal of presenting limitations is to provide meaningful information to the reader; however, too often, limitations in medical education articles are overlooked or reduced to simplistic and minimally relevant themes (e.g., single institution study, use of self-reported data, or small sample size) [ 1 ]. This issue is prominent in other fields of inquiry in medicine as well. For example, despite the clinical implications, medical studies often fail to discuss how limitations could have affected the study findings and interpretations [ 2 ]. Further, observational research often fails to remind readers of the fundamental limitation inherent in the study design, which is the inability to attribute causation [ 3 ]. By reporting generic limitations or omitting them altogether, researchers miss opportunities to fully communicate the relevance of their work, illustrate how their work advances a larger field under study, and suggest potential areas for further investigation.

Goals of presenting limitations

Medical education scholarship should provide empirical evidence that deepens our knowledge and understanding of education [ 4 , 5 ], informs educational practice and process, [ 6 , 7 ] and serves as a forum for educating other researchers [ 8 ]. Providing study limitations is indeed an important part of this scholarly process. Without them, research consumers are pressed to fully grasp the potential exclusion areas or other biases that may affect the results and conclusions provided [ 9 ]. Study limitations should leave the reader thinking about opportunities to engage in prospective improvements [ 9 – 11 ] by presenting gaps in the current research and extant literature, thereby cultivating other researchers’ curiosity and interest in expanding the line of scholarly inquiry [ 9 ].

Presenting study limitations is also an ethical element of scientific inquiry [ 12 ]. It ensures transparency of both the research and the researchers [ 10 , 13 , 14 ], as well as provides transferability [ 15 ] and reproducibility of methods. Presenting limitations also supports proper interpretation and validity of the findings [ 16 ]. A study’s limitations should place research findings within their proper context to ensure readers are fully able to discern the credibility of a study’s conclusion, and can generalize findings appropriately [ 16 ].

Why some authors may fail to present limitations

As Price and Murnan [ 8 ] note, there may be overriding reasons why researchers do not sufficiently report the limitations of their study. For example, authors may not fully understand the importance and implications of their study’s limitations or assume that not discussing them may increase the likelihood of publication. Word limits imposed by journals may also prevent authors from providing thorough descriptions of their study’s limitations [ 17 ]. Still another possible reason for excluding limitations is a diffusion of responsibility in which some authors may incorrectly assume that the journal editor is responsible for identifying limitations. Regardless of reason or intent, researchers have an obligation to the academic community to present complete and honest study limitations.

A guide to presenting limitations

The presentation of limitations should describe the potential limitations, explain the implication of the limitations, provide possible alternative approaches, and describe steps taken to mitigate the limitations. Too often, authors only list the potential limitations, without including these other important elements.

Describe the limitations

When describing limitations authors should identify the limitation type to clearly introduce the limitation and specify the origin of the limitation. This helps to ensure readers are able to interpret and generalize findings appropriately. Here we outline various limitation types that can occur at different stages of the research process.

Study design

Some study limitations originate from conscious choices made by the researcher (also known as delimitations) to narrow the scope of the study [ 1 , 8 , 18 ]. For example, the researcher may have designed the study for a particular age group, sex, race, ethnicity, geographically defined region, or some other attribute that would limit to whom the findings can be generalized. Such delimitations involve conscious exclusionary and inclusionary decisions made during the development of the study plan, which may represent a systematic bias intentionally introduced into the study design or instrument by the researcher [ 8 ]. The clear description and delineation of delimitations and limitations will assist editors and reviewers in understanding any methodological issues.

Data collection

Study limitations can also be introduced during data collection. An unintentional consequence of human subjects research is the potential of the researcher to influence how participants respond to their questions. Even when appropriate methods for sampling have been employed, some studies remain limited by the use of data collected only from participants who decided to enrol in the study (self-selection bias) [ 11 , 19 ]. In some cases, participants may provide biased input by responding to questions they believe are favourable to the researcher rather than their authentic response (social desirability bias) [ 20 – 22 ]. Participants may influence the data collected by changing their behaviour when they are knowingly being observed (Hawthorne effect) [ 23 ]. Researchers—in their role as an observer—may also bias the data they collect by allowing a first impression of the participant to be influenced by a single characteristic or impression of another characteristic either unfavourably (horns effect) or favourably (halo effort) [ 24 ].

Data analysis

Study limitations may arise as a consequence of the type of statistical analysis performed. Some studies may not follow the basic tenets of inferential statistical analyses when they use convenience sampling (i.e. non-probability sampling) rather than employing probability sampling from a target population [ 19 ]. Another limitation that can arise during statistical analyses occurs when studies employ unplanned post-hoc data analyses that were not specified before the initial analysis [ 25 ]. Unplanned post-hoc analysis may lead to statistical relationships that suggest associations but are no more than coincidental findings [ 23 ]. Therefore, when unplanned post-hoc analyses are conducted, this should be clearly stated to allow the reader to make proper interpretation and conclusions—especially when only a subset of the original sample is investigated [ 23 ].

Study results

The limitations of any research study will be rooted in the validity of its results—specifically threats to internal or external validity [ 8 ]. Internal validity refers to reliability or accuracy of the study results [ 26 ], while external validity pertains to the generalizability of results from the study’s sample to the larger, target population [ 8 ].

Examples of threats to internal validity include: effects of events external to the study (history), changes in participants due to time instead of the studied effect (maturation), systematic reduction in participants related to a feature of the study (attrition), changes in participant responses due to repeatedly measuring participants (testing effect), modifications to the instrument (instrumentality) and selecting participants based on extreme scores that will regress towards the mean in repeat tests (regression to the mean) [ 27 ].

Threats to external validity include factors that might inhibit generalizability of results from the study’s sample to the larger, target population [ 8 , 27 ]. External validity is challenged when results from a study cannot be generalized to its larger population or to similar populations in terms of the context, setting, participants and time [ 18 ]. Therefore, limitations should be made transparent in the results to inform research consumers of any known or potentially hidden biases that may have affected the study and prevent generalization beyond the study parameters.

Explain the implication(s) of each limitation

Authors should include the potential impact of the limitations (e.g., likelihood, magnitude) [ 13 ] as well as address specific validity implications of the results and subsequent conclusions [ 16 , 28 ]. For example, self-reported data may lead to inaccuracies (e.g. due to social desirability bias) which threatens internal validity [ 19 ]. Even a researcher’s inappropriate attribution to a characteristic or outcome (e.g., stereotyping) can overemphasize (either positively or negatively) unrelated characteristics or outcomes (halo or horns effect) and impact the internal validity [ 24 ]. Participants’ awareness that they are part of a research study can also influence outcomes (Hawthorne effect) and limit external validity of findings [ 23 ]. External validity may also be threatened should the respondents’ propensity for participation be correlated with the substantive topic of study, as data will be biased and not represent the population of interest (self-selection bias) [ 29 ]. Having this explanation helps readers interpret the results and generalize the applicability of the results for their own setting.

Provide potential alternative approaches and explanations

Often, researchers use other studies’ limitations as the first step in formulating new research questions and shaping the next phase of research. Therefore, it is important for readers to understand why potential alternative approaches (e.g. approaches taken by others exploring similar topics) were not taken. In addition to alternative approaches, authors can also present alternative explanations for their own study’s findings [ 13 ]. This information is valuable coming from the researcher because of the direct, relevant experience and insight gained as they conducted the study. The presentation of alternative approaches represents a major contribution to the scholarly community.

Describe steps taken to minimize each limitation

No research design is perfect and free from explicit and implicit biases; however various methods can be employed to minimize the impact of study limitations. Some suggested steps to mitigate or minimize the limitations mentioned above include using neutral questions, randomized response technique, force choice items, or self-administered questionnaires to reduce respondents’ discomfort when answering sensitive questions (social desirability bias) [ 21 ]; using unobtrusive data collection measures (e.g., use of secondary data) that do not require the researcher to be present (Hawthorne effect) [ 11 , 30 ]; using standardized rubrics and objective assessment forms with clearly defined scoring instructions to minimize researcher bias, or making rater adjustments to assessment scores to account for rater tendencies (halo or horns effect) [ 24 ]; or using existing data or control groups (self-selection bias) [ 11 , 30 ]. When appropriate, researchers should provide sufficient evidence that demonstrates the steps taken to mitigate limitations as part of their study design [ 13 ].

In conclusion, authors may be limiting the impact of their research by neglecting or providing abbreviated and generic limitations. We present several examples of limitations to consider; however, this should not be considered an exhaustive list nor should these examples be added to the growing list of generic and overused limitations. Instead, careful thought should go into presenting limitations after research has concluded and the major findings have been described. Limitations help focus the reader on key findings, therefore it is important to only address the most salient limitations of the study [ 17 , 28 ] related to the specific research problem, not general limitations of most studies [ 1 ]. It is important not to minimize the limitations of study design or results. Rather, results, including their limitations, must help readers draw connections between current research and the extant literature.

The quality and rigor of our research is largely defined by our limitations [ 31 ]. In fact, one of the top reasons reviewers report recommending acceptance of medical education research manuscripts involves limitations—specifically how the study’s interpretation accounts for its limitations [ 32 ]. Therefore, it is not only best for authors to acknowledge their study’s limitations rather than to have them identified by an editor or reviewer, but proper framing and presentation of limitations can actually increase the likelihood of acceptance. Perhaps, these issues could be ameliorated if academic and research organizations adopted policies and/or expectations to guide authors in proper description of limitations.

How To Write Scope and Delimitation of a Research Paper (With Examples)

An effective research paper or thesis has a well-written Scope and Delimitation.  This portion specifies your study’s coverage and boundaries.

Not yet sure about how to write your research’s Scope and Delimitation? Fret not, as we’ll guide you through the entire writing process through this article.

Related: How To Write Significance of the Study (With Examples)

Table of Contents

What is the scope and delimitation of a research paper.

The “Scope and Delimitation” section states the concepts and variables your study covered. It tells readers which things you have included and excluded in your analysis.

This portion tells two things: 1

• The study’s “Scope” – concepts and variables you have explored in your research and;
• The study’s “Delimitation” – the “boundaries” of your study’s scope. It sets apart the things included in your analysis from those excluded.

For example, your scope might be the effectiveness of plant leaves in lowering blood sugar levels. You can “delimit” your study only to the effect of gabi leaves on the blood glucose of Swiss mice.

Where Should I Put the Scope and Delimitation?

This portion is in Chapter 1, usually after the “Background of the Study.”

Why Should I Write the Scope and Delimitation of My Research Paper?

There’s a lot to discover in a research paper or thesis. However, your resources and time dedicated to it are scarce. Thus, given these constraints, you have to narrow down your study. You do this in the Scope and Delimitation.

Suppose you’re studying the correlation between the quantity of organic fertilizer and plant growth . Experimenting with several types of plants is impossible because of several limitations. So, you’ve decided to use one plant type only. 

Informing your readers about this decision is a must. So, you have to state it in your Scope and Delimitation. It also acts as a “disclaimer” that your results are inapplicable to the entire plant kingdom.

What Is the Difference Between Delimitation and Limitation?

People often use the terms “Delimitation” and “Limitation” interchangeably. However, these words differ 2 .

Delimitation refers to factors you set to limit your analysis. It delineates those that are included in your research and those that are excluded. Remember, delimitations are within your control. 

Meanwhile, limitations are factors beyond your control that may affect your research’s results.  You can think of limitations as the “weaknesses” of your study. 

Let’s go back to our previous example. Due to some constraints, you’ve only decided to examine one plant type: dandelions. This is an example of a delimitation since it limits your analysis to dandelions only and not other plant types. Note that the number of plant types used is within your control. 

Meanwhile, your study cannot state that a higher quantity of organic fertilizer is the sole reason for plant growth. That’s because your research’s focus is only on correlation. Since this is already beyond your control, then this is a limitation. 

How To Write Scope and Delimitation: Step-by-Step Guide

To write your research’s Scope and Delimitation section, follow these steps:

1. Review Your Study’s Objectives and Problem Statement

Your study’s coverage relies on its objectives. Thus, you can only write this section if you know what you’re researching. Furthermore, ensure that you understand the problems you ought to answer. 

Once you understand the abovementioned things, you may start writing your study’s Scope and Delimitation.

2. State the Key Information To Explain Your Study’s Coverage and Boundaries

a. The Main Objective of the Research

This refers to the concept that you’re focusing on in your research. Some examples are the following:

• level of awareness or satisfaction of a particular group of people
• correlation between two variables
• effectiveness of a new product
• comparison between two methods/approaches
• lived experiences of several individuals

It’s helpful to consult your study’s Objectives or Statement of the Problem section to determine your research’s primary goal.

b. Independent and Dependent Variables Included

Your study’s independent variable is the variable that you manipulate. Meanwhile, the dependent variable is the variable whose result depends upon the independent variable. Both of these variables must be clear and specific when indicated. 

Suppose you study the relationship between social media usage and students’ language skills. These are the possible variables for the study:

• Independent Variable: Number of hours per day spent on using Facebook
• Dependent Variable: Grade 10 students’ scores in Quarterly Examination in English. 

Note how specific the variables stated above are. For the independent variable, we narrow it down to Facebook only. Since there are many ways to assess “language skills,” we zero in on the students’ English exam scores as our dependent variable. 

c. Subject of the Study

This refers to your study’s respondents or participants. 

In our previous example, the research participants are Grade 10 students. However, there are a lot of Grade 10 students in the Philippines. Thus, we have to select from a specific school only—for instance, Grade 10 students from a national high school in Manila. 

d. Timeframe and Location of the Study

Specify the month(s), quarter(s), or year(s) as the duration of your study. Also, indicate where you will gather the data required for your research. 

e. Brief Description of the Study’s Research Design and Methodology

You may also include whether your research is quantitative or qualitative, the sampling method (cluster, stratified, purposive) applied, and how you conducted the experiment.

Using our previous example, the Grade 10 students can be selected using stratified sampling. Afterward, the researchers may obtain their English quarterly exam scores from their respective teachers. You can add these things to your study’s Scope and Delimitation. 

3. Indicate Which Variables or Factors Are Not Covered by Your Research

Although you’ve already set your study’s coverage and boundaries in Step 2, you may also explicitly mention things you’ve excluded from your research. 

Returning to our previous example, you can state that your assessment will not include the vocabulary and oral aspects of the English proficiency skill. 

Examples of Scope and Delimitation of a Research Paper

1. scope and delimitation examples for quantitative research.

a. Example 1

Research Title

    A Study on the Relationship of the Extent of Facebook Usage on the English Proficiency Level of Grade 10 Students of Matagumpay High School

Scope and Delimitation

(Main Objective)

This study assessed the correlation between the respondents’ duration of Facebook usage and their English proficiency level. 

(Variables used)

The researchers used the number of hours per day of using Facebook and the activities usually performed on the platform to assess the respondents’ extent of Facebook usage. Meanwhile, the respondents’ English proficiency level is limited to their quarterly English exam scores. 

(Subject of the study)

A sample of fifty (50) Grade 10 students of Matagumpay High School served as the study’s respondents. 

(Timeframe and location)

This study was conducted during the Second Semester of the School Year 2018 – 2019 on the premises of Matagumpay High School in Metro Manila. 

(Methodology)

The respondents are selected by performing stratified random sampling to ensure that there will be ten respondents from five Grade 10 classes of the school mentioned above. The researchers administered a 20-item questionnaire to assess the extent of Facebook usage of the selected respondents. Meanwhile, the data for the respondents’ quarterly exam scores were acquired from their English teachers. The collected data are handled with the utmost confidentiality. Spearman’s Rank Order Correlation was applied to quantitatively assess the correlation between the variables.

(Exclusions)

This study didn’t assess other aspects of the respondents’ English proficiency, such as English vocabulary and oral skills. 

Note: The words inside the parentheses in the example above are guides only. They are not included in the actual text.

b. Example 2

  Level of Satisfaction of Grade 11 Students on the Implementation of the Online Learning Setup of Matagumpay High School for SY 2020 – 2021

This study aims to identify students’ satisfaction levels with implementing online learning setups during the height of the COVID-19 pandemic.

Students’ satisfaction was assessed according to teachers’ pedagogy, school policies, and learning materials used in the online learning setup. The respondents included sixty (60) Grade 11 students of Matagumpay High School who were randomly picked. The researchers conducted the study from October 2020 to February 2021. 

Online platforms such as email and social media applications were used to reach the respondents. The researchers administered a 15-item online questionnaire to measure the respondents’ satisfaction levels. Each response was assessed using a Likert Scale to provide a descriptive interpretation of their answers. A weighted mean was applied to determine the respondents’ general satisfaction. 

This study did not cover other factors related to the online learning setup, such as the learning platform used, the schedule of synchronous learning, and channels for information dissemination.

2. Scope and Delimitation Examples for Qualitative Research

  Lived Experiences of Public Utility Vehicle (PUV) Drivers of Antipolo City Amidst the Continuous June 2022 Oil Price Hikes

This research focused on the presentation and discussion of the lived experiences of PUV drivers during the constant oil price hike in June 2022.

The respondents involved are five (5) jeepney drivers from Antipolo City who agreed to be interviewed. The researchers assessed their experiences in terms of the following: (1) daily net income; (2) duration and extent of working; (3) alternative employment opportunity considerations; and (4) mental and emotional status. The respondents were interviewed daily at their stations on June 6 – 10, 2022. 

In-depth one-on-one interviews were used for data collection.  Afterward, the respondents’ first-hand experiences were drafted and annotated with the researchers’ insights. 

The researchers excluded some factors in determining the respondents’ experiences, such as physical and health conditions and current family relationship status. 

 A Study on the Perception of the Residents of Mayamot, Antipolo City on the Political and Socioeconomic Conditions During the Post-EDSA Period (1986 – 1996)

This research aims to discuss the perception of Filipinos regarding the political and socioeconomic economic conditions during the post-EDSA period, specifically during the years 1986 – 1996. 

Ten (10) residents of Mayamot, Antipolo City, who belonged to Generation X (currently 40 – 62 years old), were purposively selected as the study’s respondents. The researchers asked them about their perception of the following aspects during the period mentioned above (1) performance of national and local government; (2) bureaucracy and government services; (3) personal economic and financial status; and (4) wage purchasing power. 

The researchers conducted face-to-face interviews in the respondents’ residences during the second semester of AY 2018 – 2019. The responses were written and corroborated with the literature on the post-EDSA period. 

The following factors were not included in the research analysis: political conflicts and turmoils, the status of the legislative and judicial departments, and other macroeconomic indicators. 

Tips and Warnings

1. use the “5ws and 1h” as your guide in understanding your study’s coverage.

• Why did you write your study?  
• What variables are included?
• Who are your study’s subject
• Where did you conduct the study?
• When did your study start and end?
• How did you conduct the study?

2. Use key phrases when writing your research’s scope

• This study aims to … 
• This study primarily focuses on …
• This study deals with … 
• This study will cover …
• This study will be confined…

3. Use key phrases when writing factors beyond your research’s delimitations

• The researcher(s) decided to exclude …
• This study did not cover….
• This study excluded … 
• These variables/factors were excluded from the study…

4. Don’t forget to ask for help

Your research adviser can assist you in selecting specific concepts and variables suitable to your study. Make sure to consult him/her regularly. 

5. Make it brief

No need to make this section wordy. You’re good to go if you meet the “5Ws and 1Hs”. 

Frequently Asked Questions

1. what are scope and delimitation in tagalog.

In a Filipino research ( pananaliksik ), Scope and Delimitation is called “ Saklaw at Delimitasyon”. 

Here’s an example of Scope and Delimitation in Filipino:

Pamagat ng Pananaliksik

Epekto Ng Paggamit Ng Mga Digital Learning Tools Sa Pag-Aaral Ng Mga Mag-Aaral Ng Mataas Na Paaralan Ng Matagumpay Sa General Mathematics

Sakop at Delimitasyon ng Pag-aaral

Nakatuon ang pananaliksik na ito sa epekto ng paggamit ng mga digital learning aids sa pag-aaral ng mga mag-aaral.

Ang mga digital learning tools na kinonsidera sa pag-aaral na ito ay Google Classroom, Edmodo, Kahoot, at mga piling bidyo mula YouTube. Samantala, ang epekto sa pag-aaral ng mga mag-aaral ng mga nabanggit na digital learning tools ay natukoy sa pamamagitan ng kanilang (1) mga pananaw hinggil sa benepisyo nito sa kanilang pag-aaral sa General Mathematics at (2) kanilang average grade sa asignaturang ito.

Dalawampu’t-limang (25) mag-aaral mula sa Senior High School ng Mataas na Paaralan ng Matagumpay ang pinili para sa pananaliksik na ito. Sila ay na-interbyu at binigyan ng questionnaire noong Enero 2022 sa nasabing paaralan. Sinuri ang resulta ng pananaliksik sa pamamagitan ng mga instrumentong estadistikal na weighted mean at Analysis of Variance (ANOVA). Hindi saklaw ng pananaliksik na ito ang ibang mga aspeto hinggil sa epekto ng online learning aids sa pag-aaral gaya ng lebel ng pag-unawa sa aralin at kakayahang iugnay ito sa araw-araw na buhay. 

2. The Scope and Delimitation should consist of how many paragraphs?

Three or more paragraphs will suffice for your study’s Scope and Delimitation. Here’s our suggestion on what you should write for each paragraph:

Paragraph 1: Introduction (state research objective) Paragraph 2: Coverage and boundaries of the research (you may divide this section into 2-3 paragraphs) Paragraph 3 : Factors excluded from the study

• University of St. La Salle. Unit 3: Lesson 3 Setting the Scope and Limitation of a Qualitative Research [Ebook] (p. 12). Retrieved from https://www.studocu.com/ph/document/university-of-st-la-salle/senior-high-school/final-sg-pr1-11-12-unit-3-lesson-3-setting-the-scope-and-limitation-of-a-qualitative-research/24341582
• Theofanidis, D., & Fountouki, A. (2018). Limitations and Delimitations in the Research Process. Perioperative Nursing (GORNA), 7(3), 155–162. doi: 10.5281/zenodo.2552022

Written by Jewel Kyle Fabula

in Career and Education , Juander How

Jewel Kyle Fabula

Jewel Kyle Fabula is a Bachelor of Science in Economics student at the University of the Philippines Diliman. His passion for learning mathematics developed as he competed in some mathematics competitions during his Junior High School years. He loves cats, playing video games, and listening to music.

Browse all articles written by Jewel Kyle Fabula

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Writing Limitations of Research Study — 4 Reasons Why It Is Important!

It is not unusual for researchers to come across the term limitations of research during their academic paper writing. More often this is interpreted as something terrible. However, when it comes to research study, limitations can help structure the research study better. Therefore, do not underestimate significance of limitations of research study.

Allow us to take you through the context of how to evaluate the limits of your research and conclude an impactful relevance to your results.

Table of Contents

What Are the Limitations of a Research Study?

Every research has its limit and these limitations arise due to restrictions in methodology or research design.  This could impact your entire research or the research paper you wish to publish. Unfortunately, most researchers choose not to discuss their limitations of research fearing it will affect the value of their article in the eyes of readers.

However, it is very important to discuss your study limitations and show it to your target audience (other researchers, journal editors, peer reviewers etc.). It is very important that you provide an explanation of how your research limitations may affect the conclusions and opinions drawn from your research. Moreover, when as an author you state the limitations of research, it shows that you have investigated all the weaknesses of your study and have a deep understanding of the subject. Being honest could impress your readers and mark your study as a sincere effort in research.

Why and Where Should You Include the Research Limitations?

The main goal of your research is to address your research objectives. Conduct experiments, get results and explain those results, and finally justify your research question . It is best to mention the limitations of research in the discussion paragraph of your research article.

At the very beginning of this paragraph, immediately after highlighting the strengths of the research methodology, you should write down your limitations. You can discuss specific points from your research limitations as suggestions for further research in the conclusion of your thesis.

1. Common Limitations of the Researchers

Limitations that are related to the researcher must be mentioned. This will help you gain transparency with your readers. Furthermore, you could provide suggestions on decreasing these limitations in you and your future studies.

2. Limited Access to Information

Your work may involve some institutions and individuals in research, and sometimes you may have problems accessing these institutions. Therefore, you need to redesign and rewrite your work. You must explain your readers the reason for limited access.

3. Limited Time

All researchers are bound by their deadlines when it comes to completing their studies. Sometimes, time constraints can affect your research negatively. However, the best practice is to acknowledge it and mention a requirement for future study to solve the research problem in a better way.

4. Conflict over Biased Views and Personal Issues

Biased views can affect the research. In fact, researchers end up choosing only those results and data that support their main argument, keeping aside the other loose ends of the research.

Types of Limitations of Research

Before beginning your research study, know that there are certain limitations to what you are testing or possible research results. There are different types that researchers may encounter, and they all have unique characteristics, such as:

1. Research Design Limitations

Certain restrictions on your research or available procedures may affect your final results or research outputs. You may have formulated research goals and objectives too broadly. However, this can help you understand how you can narrow down the formulation of research goals and objectives, thereby increasing the focus of your study.

2. Impact Limitations

Even if your research has excellent statistics and a strong design, it can suffer from the influence of the following factors:

• Presence of increasing findings as researched
• Being population specific
• A strong regional focus.

3. Data or statistical limitations

In some cases, it is impossible to collect sufficient data for research or very difficult to get access to the data. This could lead to incomplete conclusion to your study. Moreover, this insufficiency in data could be the outcome of your study design. The unclear, shabby research outline could produce more problems in interpreting your findings.

How to Correctly Structure Your Research Limitations?

There are strict guidelines for narrowing down research questions, wherein you could justify and explain potential weaknesses of your academic paper. You could go through these basic steps to get a well-structured clarity of research limitations:

• Declare that you wish to identify your limitations of research and explain their importance,
• Provide the necessary depth, explain their nature, and justify your study choices.
• Write how you are suggesting that it is possible to overcome them in the future.

In this section, your readers will see that you are aware of the potential weaknesses in your business, understand them and offer effective solutions, and it will positively strengthen your article as you clarify all limitations of research to your target audience.

Know that you cannot be perfect and there is no individual without flaws. You could use the limitations of research as a great opportunity to take on a new challenge and improve the future of research. In a typical academic paper, research limitations may relate to:

1. Formulating your goals and objectives

If you formulate goals and objectives too broadly, your work will have some shortcomings. In this case, specify effective methods or ways to narrow down the formula of goals and aim to increase your level of study focus.

2. Application of your data collection methods in research

If you do not have experience in primary data collection, there is a risk that there will be flaws in the implementation of your methods. It is necessary to accept this, and learn and educate yourself to understand data collection methods.

3. Sample sizes

This depends on the nature of problem you choose. Sample size is of a greater importance in quantitative studies as opposed to qualitative ones. If your sample size is too small, statistical tests cannot identify significant relationships or connections within a given data set.

You could point out that other researchers should base the same study on a larger sample size to get more accurate results.

4. The absence of previous studies in the field you have chosen

Writing a literature review is an important step in any scientific study because it helps researchers determine the scope of current work in the chosen field. It is a major foundation for any researcher who must use them to achieve a set of specific goals or objectives.

However, if you are focused on the most current and evolving research problem or a very narrow research problem, there may be very little prior research on your topic. For example, if you chose to explore the role of Bitcoin as the currency of the future, you may not find tons of scientific papers addressing the research problem as Bitcoins are only a new phenomenon.

It is important that you learn to identify research limitations examples at each step. Whatever field you choose, feel free to add the shortcoming of your work. This is mainly because you do not have many years of experience writing scientific papers or completing complex work. Therefore, the depth and scope of your discussions may be compromised at different levels compared to academics with a lot of expertise. Include specific points from limitations of research. Use them as suggestions for the future.

Have you ever faced a challenge of writing the limitations of research study in your paper? How did you overcome it? What ways did you follow? Were they beneficial? Let us know in the comments below!

Frequently Asked Questions

Setting limitations in our study helps to clarify the outcomes drawn from our research and enhance understanding of the subject. Moreover, it shows that the author has investigated all the weaknesses in the study.

Scope is the range and limitations of a research project which are set to define the boundaries of a project. Limitations are the impacts on the overall study due to the constraints on the research design.

Limitation in research is an impact of a constraint on the research design in the overall study. They are the flaws or weaknesses in the study, which may influence the outcome of the research.

1. Limitations in research can be written as follows: Formulate your goals and objectives 2. Analyze the chosen data collection method and the sample sizes 3. Identify your limitations of research and explain their importance 4. Provide the necessary depth, explain their nature, and justify your study choices 5. Write how you are suggesting that it is possible to overcome them in the future

Excellent article ,,,it has helped me big

This is very helpful information. It has given me an insight on how to go about my study limitations.

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Home » Limitations in Research – Types, Examples and Writing Guide

Limitations in Research – Types, Examples and Writing Guide

Table of Contents

Limitations in Research

Limitations in research refer to the factors that may affect the results, conclusions , and generalizability of a study. These limitations can arise from various sources, such as the design of the study, the sampling methods used, the measurement tools employed, and the limitations of the data analysis techniques.

Types of Limitations in Research

Types of Limitations in Research are as follows:

Sample Size Limitations

This refers to the size of the group of people or subjects that are being studied. If the sample size is too small, then the results may not be representative of the population being studied. This can lead to a lack of generalizability of the results.

Time Limitations

Time limitations can be a constraint on the research process . This could mean that the study is unable to be conducted for a long enough period of time to observe the long-term effects of an intervention, or to collect enough data to draw accurate conclusions.

Selection Bias

This refers to a type of bias that can occur when the selection of participants in a study is not random. This can lead to a biased sample that is not representative of the population being studied.

Confounding Variables

Confounding variables are factors that can influence the outcome of a study, but are not being measured or controlled for. These can lead to inaccurate conclusions or a lack of clarity in the results.

Measurement Error

This refers to inaccuracies in the measurement of variables, such as using a faulty instrument or scale. This can lead to inaccurate results or a lack of validity in the study.

Ethical Limitations

Ethical limitations refer to the ethical constraints placed on research studies. For example, certain studies may not be allowed to be conducted due to ethical concerns, such as studies that involve harm to participants.

Examples of Limitations in Research

Some Examples of Limitations in Research are as follows:

Research Title: “The Effectiveness of Machine Learning Algorithms in Predicting Customer Behavior”

Limitations:

• The study only considered a limited number of machine learning algorithms and did not explore the effectiveness of other algorithms.
• The study used a specific dataset, which may not be representative of all customer behaviors or demographics.
• The study did not consider the potential ethical implications of using machine learning algorithms in predicting customer behavior.

Research Title: “The Impact of Online Learning on Student Performance in Computer Science Courses”

• The study was conducted during the COVID-19 pandemic, which may have affected the results due to the unique circumstances of remote learning.
• The study only included students from a single university, which may limit the generalizability of the findings to other institutions.
• The study did not consider the impact of individual differences, such as prior knowledge or motivation, on student performance in online learning environments.

Research Title: “The Effect of Gamification on User Engagement in Mobile Health Applications”

• The study only tested a specific gamification strategy and did not explore the effectiveness of other gamification techniques.
• The study relied on self-reported measures of user engagement, which may be subject to social desirability bias or measurement errors.
• The study only included a specific demographic group (e.g., young adults) and may not be generalizable to other populations with different preferences or needs.

How to Write Limitations in Research

When writing about the limitations of a research study, it is important to be honest and clear about the potential weaknesses of your work. Here are some tips for writing about limitations in research:

• Identify the limitations: Start by identifying the potential limitations of your research. These may include sample size, selection bias, measurement error, or other issues that could affect the validity and reliability of your findings.
• Be honest and objective: When describing the limitations of your research, be honest and objective. Do not try to minimize or downplay the limitations, but also do not exaggerate them. Be clear and concise in your description of the limitations.
• Provide context: It is important to provide context for the limitations of your research. For example, if your sample size was small, explain why this was the case and how it may have affected your results. Providing context can help readers understand the limitations in a broader context.
• Discuss implications : Discuss the implications of the limitations for your research findings. For example, if there was a selection bias in your sample, explain how this may have affected the generalizability of your findings. This can help readers understand the limitations in terms of their impact on the overall validity of your research.
• Provide suggestions for future research : Finally, provide suggestions for future research that can address the limitations of your study. This can help readers understand how your research fits into the broader field and can provide a roadmap for future studies.

Purpose of Limitations in Research

There are several purposes of limitations in research. Here are some of the most important ones:

• To acknowledge the boundaries of the study : Limitations help to define the scope of the research project and set realistic expectations for the findings. They can help to clarify what the study is not intended to address.
• To identify potential sources of bias: Limitations can help researchers identify potential sources of bias in their research design, data collection, or analysis. This can help to improve the validity and reliability of the findings.
• To provide opportunities for future research: Limitations can highlight areas for future research and suggest avenues for further exploration. This can help to advance knowledge in a particular field.
• To demonstrate transparency and accountability: By acknowledging the limitations of their research, researchers can demonstrate transparency and accountability to their readers, peers, and funders. This can help to build trust and credibility in the research community.
• To encourage critical thinking: Limitations can encourage readers to critically evaluate the study’s findings and consider alternative explanations or interpretations. This can help to promote a more nuanced and sophisticated understanding of the topic under investigation.

When to Write Limitations in Research

Limitations should be included in research when they help to provide a more complete understanding of the study’s results and implications. A limitation is any factor that could potentially impact the accuracy, reliability, or generalizability of the study’s findings.

It is important to identify and discuss limitations in research because doing so helps to ensure that the results are interpreted appropriately and that any conclusions drawn are supported by the available evidence. Limitations can also suggest areas for future research, highlight potential biases or confounding factors that may have affected the results, and provide context for the study’s findings.

Generally, limitations should be discussed in the conclusion section of a research paper or thesis, although they may also be mentioned in other sections, such as the introduction or methods. The specific limitations that are discussed will depend on the nature of the study, the research question being investigated, and the data that was collected.

Examples of limitations that might be discussed in research include sample size limitations, data collection methods, the validity and reliability of measures used, and potential biases or confounding factors that could have affected the results. It is important to note that limitations should not be used as a justification for poor research design or methodology, but rather as a way to enhance the understanding and interpretation of the study’s findings.

Importance of Limitations in Research

Here are some reasons why limitations are important in research:

• Enhances the credibility of research: Limitations highlight the potential weaknesses and threats to validity, which helps readers to understand the scope and boundaries of the study. This improves the credibility of research by acknowledging its limitations and providing a clear picture of what can and cannot be concluded from the study.
• Facilitates replication: By highlighting the limitations, researchers can provide detailed information about the study’s methodology, data collection, and analysis. This information helps other researchers to replicate the study and test the validity of the findings, which enhances the reliability of research.
• Guides future research : Limitations provide insights into areas for future research by identifying gaps or areas that require further investigation. This can help researchers to design more comprehensive and effective studies that build on existing knowledge.
• Provides a balanced view: Limitations help to provide a balanced view of the research by highlighting both strengths and weaknesses. This ensures that readers have a clear understanding of the study’s limitations and can make informed decisions about the generalizability and applicability of the findings.

Advantages of Limitations in Research

Here are some potential advantages of limitations in research:

• Focus : Limitations can help researchers focus their study on a specific area or population, which can make the research more relevant and useful.
• Realism : Limitations can make a study more realistic by reflecting the practical constraints and challenges of conducting research in the real world.
• Innovation : Limitations can spur researchers to be more innovative and creative in their research design and methodology, as they search for ways to work around the limitations.
• Rigor : Limitations can actually increase the rigor and credibility of a study, as researchers are forced to carefully consider the potential sources of bias and error, and address them to the best of their abilities.
• Generalizability : Limitations can actually improve the generalizability of a study by ensuring that it is not overly focused on a specific sample or situation, and that the results can be applied more broadly.

About the author

Muhammad Hassan

Researcher, Academic Writer, Web developer

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• Published: 11 May 2024

A DNA barcode reference library of Croatian mosquitoes (Diptera: Culicidae): implications for identification and delimitation of species, with notes on the distribution of potential vector species

• Nataša Bušić 1 ,
• Ana Klobučar 2 ,
• Nediljko Landeka 3 ,
• Toni Žitko 4 ,
• Goran Vignjević 1 ,
• Nataša Turić 1 , 5 ,
• Mirta Sudarić Bogojević 1 ,
• Enrih Merdić 1 ,
• Mladen Kučinić 6 &
• Branka Bruvo Mađarić 7  

Parasites & Vectors volume  17 , Article number:  216 ( 2024 ) Cite this article

204 Accesses

Metrics details

Mosquitoes pose a risk to human health worldwide, and correct species identification and detection of cryptic species are the most important keys for surveillance and control of mosquito vectors. In addition to traditional identification based on morphology, DNA barcoding has recently been widely used as a complementary tool for reliable identification of mosquito species. The main objective of this study was to create a reference DNA barcode library for the Croatian mosquito fauna, which should contribute to more accurate and faster identification of species, including cryptic species, and recognition of relevant vector species.

Sampling was carried out in three biogeographical regions of Croatia over six years (2017–2022). The mosquitoes were morphologically identified; molecular identification was based on the standard barcoding region of the mitochondrial COI gene and the nuclear ITS2 region, the latter to identify species within the Anopheles maculipennis complex. The BIN-RESL algorithm assigned the COI sequences to the corresponding BINs (Barcode Index Number clusters) in BOLD, i.e. to putative MOTUs (Molecular Operational Taxonomic Units). The bPTP and ASAP species delimitation methods were applied to the genus datasets in order to verify/confirm the assignment of specimens to specific MOTUs.

A total of 405 mosquito specimens belonging to six genera and 30 morphospecies were collected and processed. Species delimitation methods assigned the samples to 31 (BIN-RESL), 30 (bPTP) and 28 (ASAP) MOTUs, with most delimited MOTUs matching the morphological identification. Some species of the genera Culex , Aedes and Anopheles were assigned to the same MOTUs, especially species that are difficult to distinguish morphologically and/or represent species complexes. In total, COI barcode sequences for 34 mosquito species and ITS2 sequences for three species of the genus Anopheles were added to the mosquito sequence database for Croatia, including one individual from the Intrudens Group, which represents a new record for the Croatian mosquito fauna.

We present the results of the first comprehensive study combining morphological and molecular identification of most mosquito species present in Croatia, including several invasive and vector species. With the exception of some closely related species, this study confirmed that DNA barcoding based on COI provides a reliable basis for the identification of mosquito species in Croatia.

Graphical Abstract

Mosquitoes are one of the most studied groups of insects in the world, mainly because of their medical and veterinary role as vectors of pathogens causing millions of deaths per year.. Although most data on mosquito-borne diseases mainly refer to tropical and subtropical countries, quite a few cases of such infections have also recently been recorded in Europe [ 1 , 2 , 3 , 4 ]. Due to increasing trade and travel, invasive mosquito species are introduced and spread very easily [ 5 , 6 , 7 ], such as Aedes albopictus and Aedes aegypti, which are vectors of many viruses that cause various infectious diseases (e.g. dengue, chikungunya, yellow fever, Japanese encephalitis, West Nile and Zika viruses) [ 8 , 9 , 10 ]. In Croatia, well established populations of Aedes albopictus are present [ 11 ], while Aedes aegypti has not yet been recorded. In 2010, autochthonous cases of dengue fever caused by the dengue virus were registered for the first time in Croatia [ 12 ]. Also, several smaller dengue epidemics were continuously registered in Europe, with a number of autochthonous cases in France, Spain and Italy [ 13 , 14 , 15 ]. Although invasive species pose a serious medical problem, native mosquito species such as those of the genus Culex should not be ignored. This has been demonstrated by recent cases of West Nile virus (WNV) outbreaks in Romania, Spain, the Netherlands, Italy, Hungary, Germany, and Serbia [ 3 , 16 , 17 , 18 ]. In Croatia, the first clinical cases of WNV infection were reported in 2012 [ 19 ], associated with Culex pipiens complex, and possibly some other species [ 20 ]. After 2012, WNV infections occurred continuously in Croatia [ 21 ]. The main vector of Usutu virus (USUV) infection is Culex pipiens , although the virus has also been found in several other species [ 22 , 23 ]. Recent studies show that USUV has become endemic in northwestern Croatia [ 24 ]. Malaria used to be a prevalent disease in Europe, but currently only imported cases are reported; no deaths occurred following autochthonous infections in 2000–2019 [ 25 ]. However, numbers of imported malaria cases in Europe have increased, leading to the re-emergence of indigenous cases in Greece, Spain, Italy, and France [ 26 , 27 , 28 , 29 ]. Within the Anopheles maculipennis complex, several species are considered vectors of malaria parasites in Europe: Anopheles atroparvus, Anopheles labranchiae, Anopheles messeae and Anopheles sacharovi [ 30 , 31 ].

The correct identification of mosquitoes is an important part of implementing effective vector management strategies. Conventional identification with dichotomous keys is essential, but has many shortcomings and is not always sufficient to identify mosquito specimens. Important features required for accurate morphological identification of mosquitoes often fall off or are damaged during sampling (scales, legs, wings), or these defining differences are only visible at a certain stage of development or are related to sex. In addition, mosquitoes often occur in complexes of closely related species, and morphological identification proved to be insufficient in most of these cases [ 32 ].

Molecular identification by DNA barcoding is an accurate method of species identification, independent of the developmental stage and condition of the specimens examined [ 33 , 34 , 35 ]. Many studies have confirmed that the standard mitochondrial COI barcoding region is a suitable marker for identification of mosquito species and recognition of cryptic species [ 36 , 37 , 38 , 39 , 40 , 41 ]. Nevertheless, for several genera and species complexes ( Culex, Aedes and Anopheles ), the use of additional molecular markers is necessary to increase identification accuracy and to distinguish between closely related species, forms and hybrids. For example, ITS2 (nuclear ribosomal internal transciber spacer 2), Ace2 gene and polymorphisms of various microsatellite loci (e.g. CQ11) are now routinely used [ 42 , 43 , 44 , 45 , 46 , 47 ]. However, despite major advances in molecular methods, accurate identification requires a multidisciplinary approach to taxonomy that includes morphological, molecular, distributional and ecological data [ 36 , 48 ].

To date, 52 species of mosquitoes have been recorded in Croatia, two of which are invasive: Aedes albopictus and Aedes japonicus [ 11 ]. Traditionally, the majority of research has been based on morphological identification, but several recently published papers have used molecular methods to confirm the presence of certain species. By these, Cx. torrentium was proven for the first time to belong to the mosquito fauna of Croatia in 2018 [ 49 ], and the presence of several other species was confirmed for certain regions of Croatia [ 50 , 51 ]. However, no systematic survey has been conducted to date that would provide an overview of the barcodes of the Croatian mosquito fauna, and there is also very little data for neighbour countries [ 52 , 53 ]. The importance of such data lies in the potential presence and spread of new invasive species that are potential arbovirus vectors, such as Aedes koreicus , which is currently established in surrounding countries but has not yet been recorded in Croatia [ 54 , 55 ]. Recent DNA barcoding studies in Europe [ 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 ] established national DNA barcode libraries for several countries, and resulted in new species findings and confirmation of unrecorded species in certain areas, as well as identification of cryptic taxonomic units [ 65 ]. Nevertheless, the number of barcode sequences of European mosquitoes with accurate country and species designation is still limited and accounts for less than 10% of all Culicidae records in BOLD (accessed December 15, 2023).

The aim of this study was to create a DNA barcode library for the Croatian mosquito fauna and to gain insight into the genetic diversity and geographical distribution of mosquito species through DNA barcoding. The data obtained will contribute to public databases (BOLD, NCBI GenBank) and help create a platform for easier, faster and more accurate identification of mosquitoes of the Croatian fauna. The results will also serve as a basis for projects on the surveillance of invasive and vector mosquitoes and control of mosquito-borne diseases in the studied region.

With its geographical location in Central Europe and the Mediterranean region, Croatia is one of the "hotspots" of European biodiversity. The high level of biodiversity in Croatia is a consequence of the diverse composition of habitats, climatic and hydrological characteristics and the complex geological history of the region.

According to Bertić et al. [ 66 ], Croatia was divided into three biogeographic regions for the purpose of this study:the Pannonian-Peripannonian region in the north and east, the central mountainous region in the middle and the Mediterranean region in the south (Fig.  1 ). From 2017 to 2022, 50 sites were sampled in the Pannonian-Peripannonian region, 38 in the central mountainous region and 52 in the Mediterranean region of Croatia (Fig.  1 ; Additional file: Table S1).

Sampling localities in ​​three biogeographic regions of Croatia: Pannonian-Peripannonian region—green dots, Mediterranean region—blue dots, and mountainous region—orange dots; high-altitude localities in the Pannonian-Peripannonian region are also marked with orange dots. Some localities may represent multiple sampling sites (details for each sample are available in the public BOLD dataset DS-CROCU2)

Mosquito collection and a priori morphological identification

Adult mosquitoes were caught with CDC traps baited with CO 2 , BG-Sentinel traps baited with BG-Lure and CO 2 and human landing catch (HLC) method. Larvae were caught individually using a dipper. The mosquitoes were morphologically identified using the identification keys of Becker et al. [ 67 ]. All specimens were stored in 96% ethanol at -20° C. The vouchers of the barcoded specimens are kept at the Josip Juraj Strossmayer University of Osijek, Department of Biology, and at the Andrija Štampar Teaching Institute of Public Health in Zagreb.

DNA extraction and amplification

DNA was extracted from single legs of adult specimens and from entire larvae using the GenEluteTM Mammalian Genomic DNA Miniprep Kit (Sigma, Taufkirchen, Germany). The protocol for rodent tail preparation as provided with the kit was followed with slight modifications (incubation in proteinase K overnight; final DNA elution in 100 µl elution solution).

For all samples, the standard barcoding region of the mitochondrial COI gene [ 34 ] was amplified using the universal primers LCO1490 and HCO2198 [ 68 ]. For certain species complexes, the COI gene marker does not provide sufficient resolution, so other genomic regions were used. For the identification of species within the Anopheles maculipennis complex, the ITS2 region was amplified with the primers 5.8S (forward) and 28S (reverse) [ 69 ]. The amplification mixtures and PCR reaction conditions for COI and ITS2 are described in Bušić et al. [ 50 ]. The PCR products were enzymatically purified using the ExoI-rSAP system (NEB, Ipswich, MA, USA) according to the manufacturer's protocol and bidirectionally sequenced at Macrogen Inc. (Amsterdam, The Netherlands) using the amplification primers.

Data analysis

The sequences of the COI and ITS2 regions were verified and edited in Geneious 8.1.4. ( https://www.geneious.com ) and subsequently deposited in the NCBI GenBank and BOLD databases (GenBank accession numbers PP694665-PP694812, BOLD ID numbers in Additional file 1 : Table S1; additional information available in public BOLD dataset DS-CROCU2). The percentage identity of the newly obtained COI and ITS2 sequences with the records in the GenBank database was checked with the BLAST tool using the Megablast algorithm ( https://blast.ncbi.nlm.nih.gov/Blast.cgi ; accessed December 15, 2023). The BOLD identification tool ( http://www.boldsystems.org/index.php/IDS_OpenIdEngine ; accessed December 15, 2023) was used to compare COI barcode sequences amplified from our samples with publicly available data in the BOLD database. Available published COI sequences of conspecific and congeneric mosquito specimens were selected from the BOLD database of public records (accessed December 15, 2023) and used for subsequent analyses.

COI and ITS2 sequences were analysed in datasets corresponding to specific genera. Multiple sequence alignments were performed with MAFFT version 7 using the "auto" strategy [ 70 ] ( https://mafft.cbrc.jp/alignment/server/index.html ; final alignments in Additional file 2: Dataset S1). Intraspecific and interspecific p-distances were calculated in MEGA 7.0.25 [ 71 ]. Maximum likelihood (ML) trees were generated on the PhyML 3.0 web server [ 72 ] ( http://www.atgc-montpellier.fr/phyml/ ), with automatic model selection by SMS (Smart Model Selection; model determined by the AIC selection criterion) [ 73 ] and aLRT SH-like support [ 74 ].

Species delimitation methods (SDMs) bPTP [ 75 ] ( https://species.h-its.org/ptp/ ) and ASAP [ 76 ] ( https://bioinfo.mnhn.fr/abi/public/asap/asapweb.html ) were applied to genus datasets to verify/confirm the assignment of specimens to specific Molecular Operational Taxonomic Units (MOTUs). As input for bPTP, the inferred ML tree was used, while for the ASAP method, the MAFFT alignment was used. In addition, the BIN-RESL algorithm (Barcode Index Number system in BOLD) [ 77 ] assigned the sequences to the corresponding BINs in BOLD. The results of the SDMs are presented in a combined ML tree that includes all newly barcoded specimens. The tree was graphically processed in FigTree v.1.4.3. ( http://tree.bio.ed.ac.uk/software/figtree/ ).

In this study, a total of 405 mosquito specimens were collected and processed; 181 specimens in the Pannonian-Peripannonian region, 122 specimens in the Mediterranean region and 102 specimens in the mountainous region of Croatia. Based on morphological identification, a total of 30 species previously recorded in Croatia were sampled, belonging to six genera ( Aedes —16 species, Anopheles —5 species, Culex —5 species, Culiseta —2 species, Coquillettidia —1 species and Orthopodomyia —1 species) (Table  1 ). For some specimens, such as those of the Aedes annulipes/cantans/excrucians and Aedes cinereus/rossicus groups or some species complexes such as the Culex pipiens and Anopheles maculipennis complexes, it was not possible to determine morphologically to which species they belonged.

The largest number of species (28) was sampled from the Pannonian-Peripannonian region, followed by the Mediterranean region (19) and the mountainous region (18). Ten species were recorded in all three regions (Additional file 1 : Table S1). One individual from the Intrudens Group (CROCU102-21) was recorded in the Pannonian-Peripannonian region (Klokočevci – Fig.  1 ) and represents new data not only for this region, but also for the Croatian fauna in general.

The success rate of COI amplification and sequencing from both directions in relation to the number of samples processed was 72.7% (197 / 271 specimens), while the percentage of successful amplification reactions of ITS2 was 98.5% (132 / 134 specimens of the Anopheles maculipennis complex). The remaining specimens were excluded from further analyses due to failed amplification or low sequence quality. A minimum of one and a maximum of 21 COI sequences were obtained per species, with an average of six.

The BIN-RESL algorithm in BOLD assigned the specimens to 31 BINs (Table  1 ), with most delineated MOTUs matching the morphological identification. Several BINs were discordant, with two or more species placed together. BIN discordance was present in the genus Aedes and the genus Anopheles , mainly in the species that were difficult to distinguish morphologically. These are the BINs with samples identified as Ae. annulipes , Ae. cantans, Ae. riparius and Ae. excrucians (BOLD:AAB1098); Ae. rossicus and Ae. cinereus (BOLD:AAP8897); Ae. caspius and Ae. zammitii (BOLD:AAB7911); An. messeae and An. daciae (BOLD:ABY8239). Barcode gap analysis in BOLD confirmed the presence of a clear barcoding gap within the public BOLD dataset DS-CROCU2 (Fig.  2 ). The concordance with the morphological identification was 98.48%.

Frequency histogram of p-distances within and between investigated mosquito species (MOTUs) for the public BOLD dataset DS-CROCU2

In 13 species, the genetic distances of the species BIN to the nearest neighbour (NN) (i.e. non-specific specimen with the lowest interspecific distance in BOLD) were higher than the maximum intraspecific genetic distances, while other species had a lower value (Table  1 ). The mean intraspecific p-distance ranged from 0% to 1.68%, calculated for MOTUs delimited with BIN-RESL. The largest intraspecific divergence was observed in BIN BOLD:AAA7067 for the species Ae. vexans (7.22%), followed by BIN BOLD:AAB2483 for An. hyrcanus (5.32%) and BIN BOLD:AAA4751 for Cx. pipiens s.l. (5.02%). Only one species, Or. pulcripalpis (BOLD:AAW9535), showed no intraspecific variability in BOLD (Table  1 ).

The ASAP method delimited 28 MOTUs (Fig.  3 ). Some species of the genera Culex, Aedes and Anopheles were assigned to the same MOTUs, mostly again the species that are difficult to distinguish morphologically (Fig.  3 ). A very similar delimitation was achieved using the bPTP method, resulting in 30 MOTUs being assigned to our dataset. Using bPTP and BIN-RESL analysis, An. claviger s.s. was subdivided into two MOTUs. Also, Cx. modestus was subdivided into two MOTUs, but only using the bPTP delimitation method. The BIN-RESL method divided Cx. torrentium and Cx. pipiens s.l. into two different BINs, while ASAP and bPTP analyses classified them to the same MOTU.

ML tree based on COI DNA sequences of the specimens sequenced in this study. Numbers on branches denote bootstrap / aLRT support values (values lower than 70% are not shown). The results of species delimitation methods (bPTP, ASAP and BIN-RESL) are shown as vertical bars on the right

Most of the morphologically identified species formed well-supported monophyletic groups in the ML tree, which mostly corresponded to the assigned BINs, with support values between 81 and 100% bootstrap / > 0.9 aLRT (Fig.  3 ). Several species appeared to be paraphyletic, including Cx. pipiens s.l. in relation to Cx. torrentium and An. daciae and An. messeae in relation to An. maculipennis s.s.

Of the 132 specimens morphologically identified as Anopheles maculipennis complex, three species were confirmed using the ITS2 sequence: An. maculipennis s.s., An. messeae and An. daciae . An. maculipennis s.s. was the predominant species with 56.06% of the samples, followed by An. messeae with 36.36% and An. daciae with 7.57% of the samples.

Based on both morphological and molecular identification, a total of 34 species were identified in this study (Table  1 ).

This work represents the first comprehensive study aimed at generating DNA barcodes for the establishment of a DNA barcode library for the Croatian mosquito fauna. Based on morphological characteristics, 30 mosquito species were identified, divided into six genera, and four more species were confirmed based on molecular data, which in total represents about 63.5% of the total number of mosquito species recorded in Croatia [ 11 ]. The validity and accuracy of the data obtained was examined using species delimitation algorithms, with various clustering methods additionally supporting the MOTUs obtained. This study shows that, in addition to morphological classification, molecular taxonomy can also be a suitable tool for the identification and delimitation of mosquito species in Croatia, as has recently been shown for many other countries [ 36 , 37 , 38 , 57 , 62 , 78 , 79 ]. The concordance of morphological and molecular identification in this study is high, which is also consistent with recent similar studies [ 38 , 62 , 80 ]. Morphological and molecular data discrepancies might be due to misidentifications, resulting in inaccurate species names for sequences in public databases [ 81 ]. This study found minimal differences in species delimitation methods, mostly for morphologically indistinguishable species. The effectiveness of barcoding was confirmed by the presence of a clear barcoding gap, which is necessary for the effective application of DNA barcodes to identify specimens and delimit species [ 62 , 82 ]. According to Meyer & Paulay [ 83 ], a barcoding gap can be defined as the difference between the mean intraspecific sequence variability and the interspecific variability for congeneric COI sequences.

Based on DNA barcode analysis, most of the species morphologically identified in this study were categorised into established groups in ML tree analysis. A few individuals in certain taxa of the genera Aedes and Anopheles , such as Ae. annulipes / cantans / excrucians , Ae. rossicus / cinereus, Ae. caspius/zammitii, and An. daciae / messeae , were grouped within the same BINs, suggesting that the COI gene may not be informative enough for distinguishing among these species. This is also confirmed by the fact that these taxa occur in similar combinations in BOLD BINs. According to recent studies, these taxa are phylogenetically very closely related, although they have different morphological characteristics [ 38 , 57 , 62 ].

The Anopheles maculipennis complex consists of several species, seven of which have been recorded to belong to the Croatian fauna [ 11 ]. In this study three of them were identified, namely An. maculipennis s.s., An. messeae and An. daciae . In the COI sequence-based species delimitation, the Anopheles maculipennis complex was divided into two different MOTUs, An. maculipennis s. s. and An. messeae/daciae, by the results of the BIN-RESL algorithm. These two BINs are mutually nearest neighbours in BOLD, with only 1.33% distance between them, while in both BINs the highest intraspecific distance is about 4% (Table  1 ). The other two delimitation methods do not support this partitioning, as they group all An. maculipennis/messeae/daciae specimens into a single MOTU, with An. messeae/daciae specimens appearing as a paraphyletic group in the ML tree with respect to the An. maculipennis s.s. samples. This confirms the highly entangled situation in this species group which requires further investigation involving other molecular markers, similar as it was observed in Sedaghat et al. [ 84 ].

A rare species within the Anopheles maculipennis complex, Anopheles melanoon , previously recorded in the Croatian areas of southern Dalmatia and Istria [ 85 ], could not be confirmed in this study, possibly due to environmental modification of its distribution area. The occurrence of this species is closely linked to areas with horse and cow stables [ 86 , 87 ], and such habitats have become quite rare. Other species within this complex previously detected in Croatia ( An. atroparvus , An. sacharovi and An. labranchiae ) [ 88 , 89 ] were also not found in other recent surveys [ 50 , 85 ]. Future studies should definitely focus on the detection of these species to confirm or exclude their current distribution in Croatia, as they are the most important malaria vectors in Europe [ 30 ].

The sibling species Cx. torrentium and Cx. pipiens s.l. can only be distinguished morphologically based on the characteristics of the male genitalia [ 67 , 90 ]. The results of this study are consistent with the results of studies in Belgium [ 57 ] and show that these two species are separated as distinct MOTUs based on the BIN-RESL method, which was not the case in another recent study [ 62 ].

In contrast, the ASAP and bPTP methods did not show sufficient discrimination between species within genetically closely related species groups such as the Culex pipiens complex or the Anopheles maculipennis complex. For each of these two groups, the species are grouped into a single MOTU according to ASAP and bPTP.

The two sibling species Anopheles claviger s.s. (Meigen) and Anopheles petragnani Del Vecchio belong to the Anopheles claviger species complex [ 67 ], but An. petragnani has not yet been recorded in the Croatian fauna [ 11 ]. Within this species complex, COI has proven to be a sufficient tool to distinguish the two species [ 62 ]. Our two An. claviger s.s. specimens formed a strongly supported clade in the ML tree according to ASAP method, but were identified as separate MOTUs using bPTP and BIN-RESL methods. The specimen CROCU199-21 from a mountainous region was grouped in a BIN BOLD:AAM4220, where a wide European distribution with larger genetic distance (max. 3.56%) is observed. Another specimen, CROCU077-21 from the Mediterranean region, was grouped in BIN BOLD:AAE3979, with a narrower distribution (mainly Iran and Kosovo) and somewhat lower distances (max. 3.15%) (Table  1 ). A third BIN in BOLD with specimens from Tajikistan and China suggests that the species, An. claviger s.s., may be divided into several cryptic species. However, An. petragnani is placed in a separate BIN, including specimens from western Europe, some of them misidentified as An. claviger .

Culex modestus is considereda potential vector of WNV [ 91 ]. In this study, two individuals of Cx. modestus were detected in the Pannonian-Peripannonian region of Croatia near wetlands. This species is considered as the main vector of WNV in similar areas of southern France [ 92 ]. Although its dispersal ability is low, it could serve as an important enzootic and, given its ornithophilic and mammalophilic biting behaviour, bridging vector in natural/rural wetlands across Europe [ 67 ]. Therefore, in order to gain insights into the genetic structure of populations in this region, it should be studied in more detail in the future, using a larger number of individuals and localities.

Currently, there is no comprehensive database for all European mosquito species of the subgenus Ochlerotatus . According to Becker et al. [ 67 ], species groups associated with European species were classified according to region (Palaearctic, Fennoscandia, Germany and former USSR), which are also mentioned in our study (see below). The differences in the classification of species within each region will remain as long as there is no global analysis of the subgenus [ 67 ].

Within the Caspius Group there are six species, Aedes berlandi , Ae. caspius , Aedes dorsalis , Aedes mariae , Ae. pulcritarsis and Ae. zammitii [ 67 ], of which only Ae. berlandi has never been recorded in Croatia. According to all species delimitation algorithms used in this study, Ae. caspius and Ae. zammitii are grouped in the same MOTU, although they can be clearly distinguished morphologically. A similar case was observed in a recent study on the territory of Spain [ 80 ] for Ae. mariae and Ae. caspius which were grouped in the same MOTU. In our study the minimum interspecific distance between Ae. zammitii and Ae. caspius was 1.15%, similar to that in the aforementioned study [ 80 ], which is value lower than values typical between species [ 33 ]. Clearly, additional analyses of other loci that may better support species delimitation are required for a more accurate separation of species within this group.

Of the Annulipes Group, Ae. annulipes, Aedes behningi, Ae. cantans, Ae. excrucians, Aedes flavescens and Ae. riparius were recorded in Croatia [ 11 , 67 ]. In general, distinction between species Ae. annulipes and Ae.cantans cannot always be accomplished with certainty based on morphological characters. Some sequences of the specimens morphologically identified as Ae. annulipes , Ae. cantans or Ae. excrucians matched the sequences in BIN: BOLD:AAB1098, which includes samples identified as Ae. annulipes/cantans or Ae. excrucians/cantans . One specimen, which had been assigned to the species Ae. behningi according to morphological characteristics, turned out to be Ae. cantans based on molecular analysis. In our ML tree, all specimens morphologically assigned to Ae. annulipes and Ae. cantans clustered into a single, well-supported clade, and all three species delimitation algorithms grouped the samples into a single MOTU. Consequently, COI proved to be an insufficient marker for distinguishing species within this species, as previously mentioned in other studies [ 38 , 57 ].

In this study, the species Ae. cinereus and Ae. rossicus are grouped in the same MOTU according to all methods of species delimitation. Some samples morphologically identified as Ae. cinereus or Ae. rossicus were also confirmed based on COI sequences, while some could no be differentiated and had to be labelled as Ae. rossicus/cinereus (Fig.  3 , Table  1 ). All individuals were collected in the Pannonian-Peripannonian region of Croatia. The taxonomic status of the species of the subgenus Aedes occurring in the Palaearctic is still unclear. Ae. cinereus, Ae. rossicus and Aedes esoensis were considered subspecies of the nominate form Ae. cinereus by Gutsevich et al. [ 93 ]. This view is not generally accepted, as Ae. cinereus and Ae. rossicus overlap strongly in Europe, the larvae often occur at the same breeding sites (which was also the case for our samples CROCU107-21, 108–21 and 109–21 from the same location and habitat—Fig.  3 , Table  1 ), and transitional forms are unknown [ 67 ]. This is also supported by the fact that these two species are often found together, with samples from this study being assigned to the same BIN (BOLD:AAP8897).

A possible new species for the Croatian fauna, detected in this work, belongs to the Intrudens Group, which includes the species Ae. diantaeus , Ae. intrudens and Ae. pullatus [ 67 ]. Morphologically, the respective sample, CROCU102-21, was incorrectly determined as Aedes punctor , but after BIN-RESL analysis it was placed in BIN BOLD:AAF2904, which includes samples mainly identified as Ae. intrudens and Ae. diantaeus . This sequence matches 99.06% with the sequence of a specimen from Russia (KC855601) and 98.96% with a specimen from Sweden (JX040505), both of which were identified as Ae. intrudens . According to our photographs (available in the BOLD dataset DS-CROCU2) and the identification key according to Becker et al. [ 67 ], our specimen also corresponded to the description of the species Ae. intrudens. The eggs of this species overwinter, and the larvae are found from early spring onwards until the beginning of summer [ 67 ], which is consistent with our finding in April. In addition, the larvae of this species develop in temporary forest pools with dead leaves on the bottom [ 67 ], supporting our observations of its habitat. Considering that one single specimen was found, future studies should focus on the rediscovery and morphological and molecular confirmation of this species so that it can be reliably included in the list of Croatian mosquito species.

This six-year study covered 63.46% of the total mosquito fauna in Croatia. The distribution of species in Croatia by region determined in this study essentially corresponds to the results of previous studies [ 11 , 50 , 51 ]. It should be emphasized that some species included in the currently valid Croatian mosquito species list [ 11 ] were last recorded a long time ago, such as species of the Anopheles maculipennis complex: An. atroparvus , An. sacharovi and An. labranchiae [ 88 , 89 , 94 ]. Efforts have been made to eliminate malaria mosquitoes over the past centuries, and habitat changes and pollution may have contributed to reducing their population or causing extinction in this area [ 95 , 96 , 97 ]. However, as these species are the main vectors of malaria in Europe [ 30 ], future research should focus on confirming their presence (or absence) in the area. Species that were not recorded in this study but had been recorded in some other recent studies [ 98 , 99 , 100 ] are monocyclic, rare or uncommon [ 67 ], such as Aedes cataphylla , Aedes leucomelas , Ae. behningi , Ae. riparius , Culex martinii , Culiseta morsitans and Culiseta subochrea . In addition, some species are linked exclusively to certain habitats and periods of occurrence, and there was a high probability that they would not be recorded in this type of research. It is necessary to focus on these rare and unrecorded species in the future so that they can be sampled specifically and thus expand the database of Croatian mosquito barcodes in BOLD.

Conclusions

With barcoding sequences for 34 Culicidae species, the results of this study represent the basis for the establishment of a reference DNA barcode library for mosquitoes in Croatia. It has been proven that barcoding is an appropriate tool for the additional identification and delimitation of species of the Croatian mosquito fauna, even for closely related species such as Cx. pipiens s.l. and Cx. torrentium , while ITS2 proved a suitable marker to differentiate closely related species within the Anopheles maculipennis complex. The inability of COI to distinguish certain biotypes or other closely related species (such as Cx. pipiens biotype molestus ; Ae. annulipes/cantans; An. messeae/ daciae ) needs to be compensated for by additional molecular markers. In the future, studies should focus on confirming the species from the Croatian mosquito fauna list that were not included in this study. For the discovered potentially new species of the Intrudens Group, targeted investigations involving sampling of individuals in all life stages are needed to substantiate their inclusion in the list of Croatian mosquito fauna. Rapid and accurate identification is a crucial step in mosquito surveillance and control, so the data here are important not only for the assessment of biodiversity and of the geographical distribution of potential vector species in the studied area. The reference barcode sequences will contribute to future research on the mosquito fauna in Croatia, neighbouring countries and Europe in general, facilitate the identification or detection of potentially misidentified or cryptic species and provide a basis for invasive and vector species surveillance and monitoring projects.

Availability of data and materials

All relevant data are within the manuscript and its additional files. All information about barcoded specimens can be found in the public BOLD dataset DS-CROCU2. The vouchers of barcoded specimens are kept in Josip Juraj Strossmayer University of Osijek, Department of Biology, and in Andrija Štampar Teaching Institute of Public Health in Zagreb. DNAs of barcoded specimens are kept in Josip Juraj Strossmayer University of Osijek, Department of Biology.

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Acknowledgements

We would like to thank Ivana Vrućina, mr.sc. and Željko Zahirović, mr.sc. (Josip Juraj Strossmayer University of Osijek) for assistance in the field while collecting samples and to Mario Dunić (Josip Juraj Strossmayer University of Osijek) for graphical assistance. We also thank two anonymous reviewers for constructive comments and suggestions.

This work has been supported by the Croatian Science Foundation under the project IP-2016–06-9988, DNA Barcoding of Diversity of Croatian Fauna (P.I. Prof. Dr. Sc. Mladen Kučinić) and by Josip Juraj Strossmayer University of Osijek project ZUP-2018–55 (P.I. Prof. Dr. Sc. Enrih Merdić) and internal project 3105–5 (P.I. Prof. Dr. Sc. Enrih Merdić).

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Nataša Bušić, Goran Vignjević, Nataša Turić, Mirta Sudarić Bogojević & Enrih Merdić

Andrija Štampar Teaching Institute of Public Health, Zagreb, Croatia

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Nediljko Landeka

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Nataša Turić

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Conception and design of the work: NB, BBM, EM, MK; samples acquisition: NB, AK, NL, TŽ, GV, NT, MSB; analyses: NB, BBM; interpretation of data: NB, BBM, EM; manuscript draft: NB, BBM; manuscript revision: AK, EM; funding acquisition: MK, EM, NB.

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Supplementary Information

13071_2024_6291_moesm1_esm.xlsx.

Supplementary Material 1: Table S1. All samples analysed in this study with their BOLD IDs, divided by regions of Croatia where they were found.

Supplementary Material 2. Dataset S1. Nucleotide alignments of COI and ITS2 datasets for all analysed specimens.

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Bušić, N., Klobučar, A., Landeka, N. et al. A DNA barcode reference library of Croatian mosquitoes (Diptera: Culicidae): implications for identification and delimitation of species, with notes on the distribution of potential vector species. Parasites Vectors 17 , 216 (2024). https://doi.org/10.1186/s13071-024-06291-9

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DOI : https://doi.org/10.1186/s13071-024-06291-9

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• Cytochrome c oxidase I (COI).
• Internal transcribed spacer 2 (ITS2).
• Species identification.
• Species delimitation.
• Cryptic species.
• Species complex.
• Invasive species.

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