Meta-Analysis in the United States: Some Observations

Over the last 25 years, meta-analysis has been widely used to study the effects of practical treatment interventions in areas that range from psychology and education to medicine and public health. The present paper first describes the impact of meta-analysis in the United States. The paper then discusses the Campbell Collaboration, a new organization aimed at fostering public policies and practices based on systematic reviews of high quality evidence. Key problems encountered by Campbell Collaboration are reviewed, including controversies over the use of nonrandomized designs, difficulties in effect size computation, and the need for new computer software to better serve needs of meta-analytic reviews in the social sciences. The paper concludes with some examples of Campbell Collaboration accomplishments to date