Perspectives on Evidence-Based Research in Education--What Works? Issues in Synthesizing Educational Program Evaluations

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Robert E. Slavin

Director of the Center for Research and Reform in Education at Johns Hopkins University, 200 W. Towsontown Boulevard, Baltimore, MD 21204; rslavin{at}jhu.edu. He is also director of the Institute for Effective Education at the University of York, in York, United Kingdom. His research focuses on comprehensive school reform, cooperative learning, research review, and evidence-based reform. Syntheses of research on educational programs have taken on increasing policy importance. Procedures for performing such syntheses must therefore produce reliable, unbiased, and meaningful information on the strength of evidence behind each program. Because evaluations of any given program are few in number, syntheses of program evaluations must focus on minimizing bias in reviews of each study. This article discusses key issues in the conduct of program evaluation syntheses: requirements for research design, sample size, adjustments for pretest differences, duration, and use of unbiased outcome measures. It also discusses the need to balance factors such as research designs, effect sizes, and numbers of studies in rating the overall strength of evidence supporting each program.

This article was written under funding from the Institute of Education Sciences, U.S. Department of Education (Grant No. R305A040082). However, any opinions expressed are those of the author and do not necessarily represent positions or policies of the institute. I would like to thank Harris Cooper, Carole Torgerson, Steven Ross, Bette Chambers, Alan Cheung, Philip Abrami, Marlene Darwin, Jon Baron, Mark Newman, and anonymous reviewers for comments on an earlier draft.

Received January 16, 2007. Revision received July 12, 2007. Revision received September 21, 2007. Accepted October 23, 2007.

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