Journal
RESEARCH SYNTHESIS METHODS
Volume 8, Issue 3, Pages 290-302Publisher
WILEY
DOI: 10.1002/jrsm.1240
Keywords
cochrane; empirical evaluation; random-effects meta-analysis; power calculations
Funding
- MRC [MC_U105260558] Funding Source: UKRI
- Medical Research Council [MC_U105260558] Funding Source: researchfish
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One of the reasons for the popularity of meta-analysis is the notion that these analyses will possess more power to detect effects than individual studies. This is inevitably the case under a fixed-effect model. However, the inclusion of the between-study variance in the random-effects model, and the need to estimate this parameter, can have unfortunate implications for this power. We develop methods for assessing the power of random-effects meta-analyses, and the average power of the individual studies that contribute to meta-analyses, so that these powers can be compared. In addition to deriving new analytical results and methods, we apply our methods to 1991 meta-analyses taken from the Cochrane Database of Systematic Reviews to retrospectively calculate their powers. We find that, in practice, 5 ormore studies are needed to reasonably consistently achieve powers from random-effects meta-analyses that are greater than the studies that contribute to them. Not only is statistical inference under the random-effects model challenging when there are very fewstudies but also lessworthwhile in such cases. The assumption thatmeta-analysis will result in an increase in power is challenged by our findings.
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