The What Works Clearinghouse (WWC) Standards Briefs explain the rules the WWC uses to evaluate the quality of studies for practitioners, researchers, and policymakers. This brief explains what baseline equivalence is and why it matters. As part of the WWC review process for certain types of studies, reviewers assess whether the intervention group…

Discusses how clinicians and researchers can critically evaluate information from efficacy studies of language intervention programs. It argues for combining both experimental and nonexperimental approaches and suggests that the use of matching in nonrandomized studies allows for comparison of groups of children participating in an intervention…