Evidence Synthesis and Systematic Reviews

There are many types of evidence synthesis projects that students undertake, from general literature reviews that are part of a paper to participation as a team member in a full systematic review or meta-analysis. Some of the aspects of a project that students and their advisors should consider when embarking on a project:

• Timeline - many evidence synthesis projects are very time intensive. For a project that should be finished in a semester or two, rapid or otherwise limited review types should be considered.
• Scope - one of the easiest ways to limit a project is to limit the scope. Rather than doing a broad topic, select a few aspects of the topic to focus a review on. Do background reading on the topic to identify key aspects and look at other reviews to see what has already been done.
• Review type - systematic and several other types of reviews require a team to mitigate bias in study selection. If a student is working on a project independently, then some other type of review should be selected. A project that follows a systematic protocol but only has one reviewr can simply be called a "structured literature review" or a review that uses a "systematized search process." CATs (Critically Appraised Topics) are another type of review that may work well, especially in clinical fields with specific questions related to practice.
• Gap analysis - doing a gap analysis is a major part of any research project, to avoid duplicating research. Gap analyses can be written up as independent projects and are sometimes referred to as scoping reviews or mapping reviews, and can be done as team or solo projects. See Evidence and Gap Map (EGM) from the Campbell Collaborative for examples of team-based reviews of this type. Gap analyses should include analysis of the quality of the studies covered as well as the topics.
• Date range - limiting searches to date ranges are a possibility for making projects more manageable, but care should be taken. It's too easy to accidentally eliminate important research with an arbitrary date limit. However, if a previously published review is being updated, or a significant milestone within the discipline occurred, then it may make sense to restrict the search to materials published after that date. This should be made explicit, for instance titling the write-up as an update or as specifically following the milestone. Any date limitations must be justified in the write-up.
• Language - while English is the language of science in the 20th and 21st centuries, a lot of research is published in other languages worldwide and a fully comprehensive search should not reject research simply because it is reported in another language. However, it is also a common exclusion, and smaller projects often do not bother to include a justification. If you do decide to limit your searching to English language materials, you should explicitly state that in your criteria. That said, the recent development of AI-assisted writing tools has made rough machine-translation much more accessible, and it may be worth considering at least reviewing non-English materials using a translation tool before rejecting them outright. You may wish to mention these materials even if you do not include them in the formal review.