<p>What research designs and methodological features qualify a study for meta-analysis and which disqualify it? What types of research reports are appropriate for the meta-analysis? What is the cultural and linguistic range of the studies to be included? By integrating and translating the current methodological and statistical work into a practical guide, the authors address these questions to provide readers with a state-of-the-art introduction to the various approaches to doing meta-analysis. </p>