How do I know if the research question for my systematic review is too broad or too narrow?
This is a challenging question to answer because some of it depends on your research team, the time that you have available to devote to the project, and what literature has already been written on your topic. You may also want to learn about how to write a well-defined research question.
If you are working on a social sciences systematic review, you may think about how your question fits into the basic who, what, when, where, how, and why framework. Some of these considerations will help offer boundaries for both your research question and your search.
If you are working on a health sciences systematic review, a good way to evaluate your research question for specificity is to use PICO to write your research question. PICO is a common way to understand and sometimes build a clinical question. Having a research question that contains most or all of these components helps narrow your search to a specific topic. It breaks down into four components:
- P = Patient/Problem (Description of patient and/or disease)
- I = Intervention (or sometimes Exposure) (Which treatment/test/medication/surgical intervention/lifestyle change are you investigating?)
- C = Comparison (What are you comparing the intervention against? Sometimes this can be a null comparison which eliminates this element of the PICO)
- O = Outcomes (What do you hope to accomplish measure, or improve?).
Please note that your search won’t include all of your PICO components. In fact, the outcomes component of your PICO is not typically included in the search because it can introduce bias into your search.
Another way to help determine whether a question is too broad or too narrow is to look at the number of search results that come back. While there is no magic number of ‘enough’ or ‘too many’ results, you may find that if your results can guide you in the direction your research goes. For example, if your topic is quite broad, and you’re finding many systematic reviews on your topic, you might consider an umbrella review, which is loosely a systematic review of systematic reviews. For a guide to other review types, view this flow chart from the Cornell University Library. You can also always reach out to the Systematic Reviews Team for a second opinion! We are happy to meet with you to discuss your project, your search, and whether the research question is too broad or too narrow.
If you need more advice on how to structure your search, please view our creating a search webinar.
For more support on systematic reviews, advanced reviews, or evidence syntheses, please visit our Systematic Reviews and Evidence Syntheses Research Subject Guide.