Traditional methods for preparing systematic reviews and syntheses of effectiveness studies rely on a limited set of methodological criteria to include studies that measure and report effects too narrowly to forward the mission of evidence-based practice. This article discusses why and how the criteria for study selection, evidence screening, and…

When causal inferences are to be synthesized across multiple studies, efforts to establish the magnitude of a causal effect should be balanced by an effort to evaluate the generalizability of the effect. The evaluation of generalizability depends on two factors that are given little attention in current syntheses: construct validity and external…