The power of statistical tests in meta-analysis

Calculations of the power of statistical tests are important in planning re search studies (including meta-analyses) and in interpreting situations in which a result has not proven to be statistically significant. The authors describe procedures to compute statistical power of fixed- and random-effec ts tests of the mean effect size, tests for heterogeneity (or variation) of effect size parameters across studies, and tests for contrasts among effec t sizes of different studies. Examples are given using 2 published meta-ana lyses. The examples illustrate that statistical power is not always high in meta-analysis.