Conventional reviews of research on the efficacy of psychological, educational, and behavioral treatments often find considerable variation in outcome among studies and, as a consequence, fail to reach firm conclusions about the overall effectiveness of the interventions in question. In contrast meta-analytic reviews show a strong, dramatic pattern of positive overall effects that cannot readily be explained as artifacts of meta-analytic technique or generalized placebo effects. Moreover, the effects are not so small that they can be dismissed as lacking practical or clinical significance. Although meta-analysis has limitations, there are good reasons to believe that its results are more credible than those of conventional reviews and to conclude that well-developed psychological, educational, and behavioral treatment is generally efficacious.

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ABSTRACT— There is no universal guideline or rule of thumb for judging the practical importance or substantive significance of a standardized effect size estimate for an intervention. Instead, one must develop empirical benchmarks of comparison that reflect the nature of the intervention being evaluated, its target population, and the outcome measure or measures being used. This approach is applied to the assessment of effect size measures for educational interventions designed to improve student academic achievement. Three types of empirical benchmarks are illustrated: (a) normative expectations for growth over time in student achievement, (b) policy‐relevant gaps in student achievement by demographic group or school performance, and (c) effect size results from past research for similar interventions and target populations. The findings can be used to help assess educational interventions, and the process of doing so can provide guidelines for how to develop and use such benchmarks in other fields.

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The effects of correctional interventions on recidivism have important public safety implications when offenders are released from probation or prison. Hundreds of studies have been conducted on those effects, some investigating punitive approaches and some investigating rehabilitation treatments. Systematic reviews (meta-analyses) of those studies, while varying greatly in coverage and technique, display remarkable consistency in their overall findings. Supervision and sanctions, at best, show modest mean reductions in recidivism and, in some instances, have the opposite effect and increase reoffense rates. The mean recidivism effects found in studies of rehabilitation treatment, by comparison, are consistently positive and relatively large. There is, however, considerable variability in those effects associated with the type of treatment, how well it is implemented, and the nature of the offenders to whom it is applied. The specific sources of that variability have not been well explored, but some principles for effective treatment have emerged. The rehabilitation treatments generally found effective in research do not characterize current correctional practice, and bridging the gap between research and practice remains a significant challenge.

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