This study examined bias reduction in the eight nonequivalent comparison group designs (NECGDs) that result from combining (a) choice of a local versus non-local comparison group, and analytic use or not of (b) a pretest measure of the study outcome and (c) a rich set of other covariates. Bias was estimated as the difference in causal estimate…

Context: Assessments of baseline equivalency of intervention and control groups, "balance," play a critical role in evaluating educational interventions. The highest What Works Clearinghouse (WWC) of the Institute of Educational Studies (IES) standard for educational studies, "Meets WWC Design Standards Without Reservations,"…

"Attrition" is the loss of sample during the course of a study. It occurs when individuals initially randomly assigned in a study are not included when researchers examine the outcome of interest. Attrition is a common issue in education research, and it occurs for many reasons. The What Works Clearinghouse (WWC) is an initiative of the…

The present study sought the views of stakeholders, including school leaders and statutory stakeholders, on the content and evaluation of a classroom-based alcohol education intervention in a Randomised Controlled Trial in Scotland and Northern Ireland. Purposive sampling was used to ensure that schools from both the Intervention and Control…

Policymakers, experts and advocates have promoted many different types of education reform over the past few decades, but what is the evidence about the efficacy of these programs? EdChoice partnered with Hanover Research to find out what research has been conducted in nine major education reform areas focusing on outcomes related to student…

Attrition occurs when members of the initial research sample are not part of the final analysis sample, such as due to missing data or leaving the study. Both the overall sample attrition and the differences in attrition between the groups can affect the statistical equivalence of the sample and create potential for bias. The WWC has given careful…

Attrition occurs when members of the initial research sample are not part of the final analysis sample, such as due to missing data or leaving the study. Both the overall sample attrition and the differences in attrition between the groups can affect the statistical equivalence of the sample and create potential for bias. The WWC has given careful…

Experimental evaluations that involve the educational system usually involve a hierarchical structure (students are nested within classrooms that are nested within schools, etc.). Concerns about contamination, where research subjects receive certain features of an intervention intended for subjects in a different experimental group, have often led…

Purpose: The past decade has seen considerable debate about how to best evaluate the efficacy of educational improvement initiatives, and members of the educational leadership research community have entered the debate with great energy. Throughout this debate, the use of randomized experiments has been a particularly contentious subject. This…

In randomized control trials (RCTs) of educational interventions, there is a growing literature on impact estimation methods to adjust for missing student outcome data using such methods as multiple imputation, the construction of nonresponse weights, casewise deletion, and maximum likelihood methods (see, for example, Allison, 2002; Graham, 2009;…

This publication contains 12 (A3 open-out) poster-style reports of teacher experimental research. The style of presentation parallels the type of preliminary reporting common at academic conferences and postgraduate events. At the same time, it aims to act as a form of short primer to introduce teachers to the basic options that there are when…