CUMULATIVE RESEARCH KNOWLEDGE AND SOCIAL-POLICY FORMULATION - THE CRITICAL ROLE OF METAANALYSIS

For many years, policymakers expressed increasing frustration with soc ial science research. On every issue there were studies arguing for di ametrically opposed conclusions. Methods of meta-analysis that correct for the effects of sampling error have shown that almost all such con flicting results were caused by sampling error. Furthermore, the effec ts of sampling error are greatly exaggerated by using significance tes t methodology. In many areas, meta-analysis has now provided dependabl e answers to the original research questions. Meta-analysis is now inc reasingly being used by policymakers, by textbook writers, and by theo rists to provide the basic facts needed to draw both practical and exp lanatory conclusions. Sophisticated meta-analysis procedures are now u sed to correct for the effects of other study imperfections, such as m easurement error, range restriction, and artificial dichotomization. I n domains where the data on artifacts are available, the effect sizes in necessarily imperfect studies have been found to be considerably un derstated. Path analysis can be applied to the findings from meta-anal ysis to yield improved causal analyses that result in both explanation of results and improved generalization of results to new settings.