Multilevel meta-analysis: A comparison with traditional meta-analytical procedures

In this article, the authors compare the multilevel meta-analysis approach with the more traditional meta-analytical approaches. After a description and comparison of the underlying models and some of the major techniques, the results of the multilevel approach are compared with those of the traditional approaches, using a simulation study. The results of the simulation study suggest that the maximum likelihood multilevel approach is in general superior to the fixed-effects approaches, unless only a small number of studies is available. For models without moderators, the results of the multilevel approach, however, are not substantially different from the results of the traditional random-effects approaches.