3  Research Questions

The research questions guide much of the planning (and so, execution) of a systematic review. I say “much” because when you’re planning a systematic review and it’s not necessarily a one-shot endeavour, you will often want to anticipate as many future needs and wishes as possible, which extends your planning beyond your current research questions.

Still, any systematic review will be conducted with a specific initial goal in mind, and because that goal will often be obtaining one or more answers, the questions to be answered are a useful way to structure the planning.

These research questions will always contain one or more concepts. Each of these concepts will relate to one or more entities to extract (see below). Once you have decided on your research question, therefore, you can decide on the entities to extract.

However, in practice this process is nonlinear and iterative. Any given research question (or more accurately, any given set of entities to extract) implicitly determines the scope of the review, because the exclusion criteria are based on the research questions and the entities to extract, and the search strategy (e.g. the query) is based on the research questions, the entities to extract, and the exclusion criteria. As such, there is always some correspondence between the research question and the number of sources that your search strategy will yield (and that will have to be screened).

Therefore, you will usually develop all of these in parallel. For example, it is common to test different queries until the number of hits is feasible given the available resources. Depending on your screening capacity, you may be forced to revise and limit the scope of the research question(s). Similarly, if your query yields very few hits, you may want or need to broaden it (and therefore, broaden your research question(s)) to eventually obtain worthwhile results.

3.1 Systematic Reviews

3.2 Scoping Reviews

Research questions in scoping reviews ask what researchers did. They can concern anything from whether different geographical regions prioritize different topics, whether sample sizes increased or decreased over time, which definitions researchers use, and which measurement instruments researchers use, via things like which study designs are used to answer which types of questions and how paradigms change over time to whether shifts occurred in researchers’ underlying philosophy of science or epistemological perspectives.