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…

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…

High retention and treatment adherence are essential to ensure the quality of evidence from clinical trials. Strategies for improving these have been explored but actual rates in lifestyle intervention trials indicate challenges. This study examined the use of a motivational interviewing-informed strategy during interactive group orientations…

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…

Background: Epidemiological information on age-related cardiovascular disease in people with intellectual disability (ID) is scarce and inconclusive. We compared prevalence and incidence of cerebrovascular accident and myocardial infarction over age 50 in a residential population with ID to that in a general practice population. Method: Lifetime…

This addendum to previously published results presents alternative analyses of data from large-scale effectiveness studies of Cognitive Tutor Algebra I in middle schools and high schools. These alternative analyses produce results that are substantively the same as previously reported. We find a significant positive effect of 0.21 standard…

The teaching profession faces a shortage as well as a decline of teaching skills. A possible way to mitigate this is to implement evidence-based induction arrangements. Seventy-one schools with 338 beginning secondary education teachers were randomly allocated to an experimental or a control group. The experimental schools used induction…

Attrition occurs when study participants who were assigned to the treatment and control conditions do not provide outcome data and thus do not contribute to the estimation of the treatment effects. It is very common in experimental studies in education as illustrated, for instance, in a meta-analysis studying "the effects of attrition on baseline…

This paper introduces a variation on the post-test only cohort control design and addresses questions concerning both the methodological credibility and the practical utility of employing this design variation in evaluations of large-scale complex professional development programmes in mathematics education. The original design and design…

This paper introduces an empirical strategy to estimate dynamic treatment effects in randomized trials that provide treatment in multiple stages and in which various noncompliance problems arise such as attrition and selective transitions between treatment and control groups. Our approach is applied to the highly influential four year randomized…

The quality of research on groups has been notoriously poor. This article is an attempt to respond to the research and evaluation deficit by providing some methodological approaches that might encourage group researchers and practitioners to attempt high quality research. (Author)

The need to attend to both methodological and social concerns is demonstrated in two examples: one where the unchecked effects of the social consequences of a methodologically rigorous research design invalidated the evaluation and a second where explicit trade-offs between methodological rigor and social costs enabled the evaluation to proceed.…

Purpose: We assess the effects of racial or ethnic concordance between caregivers and interventionists on caregiver attrition, change in depression, and change in burden in a multisite randomized clinical trial. Design and Methods: Family caregivers of patients with Alzheimer's disease were randomized to intervention or control groups at six sites…

The possible biasing effects of attrition of subjects in longitudinal experiments is a problem to which social science researchers and evaluators rarely attend. A study of research on Project Follow Through, however, revealed few differences in family income or pretest scores, between students who dropped out of treatment and of comparison groups.…