Testing the Null Hypothesis in Meta-Analysis: A Comparison of Combined Probability and Confidence Interval Procedures
Combined significance tests (combined p values) and tests of the weighted mean effect size are both used to combine information across studies in meta-analysis. This article compares a combined significance test (the Stouffer test) with a test based on the weighted mean effect size as tests of the same null hypothesis. The tests are compared analytically in the case in which the within-group variances are known and compared through large-sample theory in the more usual case in which the variances are unknown. Generalizations suggested are then explored through a simulation study. This work demonstrates that the test based on the average effect size is usually more powerful than the Stouffer test unless there is a substantial negative correlation between within-study sample size and effect size. Thus the test based on the average effect size is generally preferable, and there is little reason to also calculate the Stouffer test.
Hedges, LV; Cooper, H; Bushman, BJ
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