This article reviews the origins and use of the terms quasi-experiment and natural experiment. It demonstrates how the terms conflate whether variation in the independent variable of interest falls short of random with whether researchers find, rather than intervene to create, that variation. Using the lens of assignment--the process driving…

By design, randomized experiments (XPs) rule out bias from confounded selection of participants into conditions. Quasi-experiments (QEs) are often considered second-best because they do not share this benefit. However, when results from XPs are used to generalize causal impacts, the benefit from unconfounded selection into conditions may be offset…

Over the last twenty years, education researchers have increasingly conducted randomised experiments with the goal of informing the decisions of educators and policymakers. Such experiments have generally employed broad, consequential, standardised outcome measures in the hope that this would allow decisionmakers to compare effectiveness of…

The What Works Clearinghouse (WWC) identifies existing research on educational interventions, assesses the quality of the research, and summarizes and disseminates the evidence from studies that meet WWC standards. The WWC aims to provide enough information so educators can use the research to make informed decisions in their settings. This…

Experimental studies are often employed to test the effectiveness of teaching innovations such as new pedagogy, curriculum, or learning resources. This article offers guidance on good practice in developing research designs, and in drawing conclusions from published reports. Random control trials potentially support the use of statistical…

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…

The central purpose of this article is to provide an overview of the many ways in which special educators can generate and think about causal inference to inform policy and practice. Consideration of causality across different lenses can be carried out by engaging in multiple method and mixed methods ways of thinking about inference. This article…

Evaluating the impact of complex whole-school interventions (CWSIs) is challenging. However, what evidence there is suggests that school leadership and other elements of whole-school contexts are important for pupils' attainment (Leithwood et al., 2006), suggesting that interventions aimed at changing these have significant potential to improve…

Design-based methods have recently been developed as a way to analyze data from impact evaluations of interventions, programs, and policies. The impact estimators are derived using the building blocks of experimental designs with minimal assumptions, and have good statistical properties. The methods apply to randomized controlled trials (RCTs) and…

What Works Clearinghouse (WWC) quick reviews (QRs) are designed to provide education practitioners and policymakers with timely, preliminary objective assessments of the quality of the research evidence from recently released research papers and reports that have received coverage in the media. These reviews focus primarily on studies of the…