When randomized control trials are not possible, quasi-experimental methods often represent the gold standard. One quasi-experimental method is difference-in-difference (DiD), which compares changes in outcomes before and after treatment across groups to estimate a causal effect. DiD researchers often use fairly exhaustive robustness checks to…

Underrepresentation of historically marginalized populations in clinical trials continues to threaten the validity of health intervention research. Evidence supports the merits of intercept and other proactive forms of recruitment for achieving more equitable representation. However, researchers also report lower retention and adherence to…

Background: Efficacy trials in education often possess a motivating theory of change: how and why should the desired improvement in outcomes occur as a consequence of the intervention? In scenarios with repeated measurements, certain subgroups may be more or less likely to manifest a treatment effect; the theory of change (TOC) provides guidance…

Educational stakeholders are keen to know the magnitude and importance of different interventions. However, the way evidence is communicated to support understanding of the effectiveness of an intervention is controversial. Typically studies in education have used the standardised mean difference as a measure of the impact of interventions. This…

Underlying all What Works Clearinghouse (WWC) products are WWC Study Review Guides, which are intended for use by WWC certified reviewers to assess studies against the WWC evidence standards. As part of an ongoing effort to increase transparency, promote collaboration, and encourage widespread use of the WWC standards, the Institute of Education…

This document provides step-by-step instructions on how to complete the Study Review Guide (SRG, Version S3, V2) for single-case designs (SCDs). Reviewers will complete an SRG for every What Works Clearinghouse (WWC) review. A completed SRG should be a reviewer's independent assessment of the study, relative to the criteria specified in the review…

Data-based problem solving is a hallmark of research-supported practices such as positive behavioral interventions and supports. In this study, we provided members of positive behavioral interventions and supports (PBIS) teams from 38 elementary schools with professional development focused on a research-supported problem-solving model…

Objective: This study examined the effectiveness of solution-focused brief therapy (SFBT) intervention on substance abuse and trauma-related problems. Methods: A randomized controlled trial design was used to evaluate the effectiveness of SFBT in primary substance use treatment services for child welfare involved parents in outpatient treatment…

School recess physical activity is important for adolescent s health and development, and several studies have established evidence based on cross-sectional studies that it is influenced by the environment in the schoolyard. The aim of this study was to investigate the effect and variation across schools of a school-based intervention on students…

Estimates of fidelity of implementation are essential to interpret the effects of educational interventions in randomized controlled trials (RCTs). While random assignment protects against many threats to validity, and therefore provides the best approximation to a true counterfactual condition, it does not ensure that the treatment condition…