10.7 Chapter summary

Meta-analysis is the quantitative synthesis of results from multiple studies. The need for this can arise when reviewing the literature and finding multiple papers that address the same question; or when a team of researchers has conducted multiple studies as part of a project. Meta-analysis can be performed using package metafor. All that is needed is an estimate of effect size from each study, and the precision of that estimate in the form of the standard error. The proportion of individual studies that found a significant result is not a good guide to the conclusion of the meta-analysis regarding the existence of the effect. Meta-analysis can also be used, where the number of studies is large enough, to investigate which study-level variables predict variation in the observed effect size.