Meta-analysis
Short definition
A meta-analysis is a statistical method that combines the results of several studies on the same question to produce an overall estimate of the effect, more precise than that of any single study.
In plain language
Many clinical studies are small and, on their own, give uncertain answers. A meta-analysis pools their results into a single estimate, giving more weight to larger or more precise studies, and shows whether the results are consistent with each other. It is usually part of a systematic review: for example, a review of virtual reality for procedural pain may bring together dozens of trials and calculate a common effect size.