Advantages of excluding underpowered studies in meta-analysis: Inclusionist versus exclusionist viewpoints

The authors propose that meta-analysts explicitly specify their research question and their standards for adequate studies to be included, using whatever standards they would have applied had they been asked to peer-review the individual studies for funding. Such a proposal corresponds to previous ones with regard to considerations of sampling, measurement, design, and analysis adequacy, but the authors of this study extend the proposal to the inclusion of the definition of adequate power. They show that if adequate power is defined and then used in reviewing studies for inclusion in a meta-analysis, excluding those that are by the meta-analysts' own criterion "underpowered," this strategy would go far toward removing bias due to the "file-drawer problem" and resulting misleading research conclusions.