Group design research studies can provide evidence to draw conclusions about "what works," "for whom," and "under what conditions" in special education. The quality indicators introduced by Gersten and colleagues (2005) have contributed to increased rigor in group design research, which has provided substantial…

Much of the evidential basis for recent policy decisions is grounded in effect size: the standardised mean difference in outcome scores between a study's intervention and comparison groups. This is interpreted as measuring educational influence, importance or effectiveness of the intervention. This article shows this is a category error at two…

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…

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…

Experimental designs that randomly assign entire clusters of individuals (e.g., schools and classrooms) to treatments are frequently advocated as a way of guarding against contamination of the estimated average causal effect of treatment. However, in the absence of contamination, experimental designs that randomly assign intact clusters to…

Despite recent findings that show fluency deficits in developmental readers, the field of developmental reading remains remiss in fluency instruction. This article provides a summary intended to increase college reading teachers' understanding of reading fluency and fluency instruction. In addition, included are the step-by-step procedures of…

This policy brief summarizes the positive results of a rigorous evaluation of Reading Partners, a widely used program that offers one-on-one tutoring provided by community volunteers to struggling readers in low-income elementary schools. A total of 1,265 students in 19 schools in three states were randomly assigned to receive Reading…

In this article, the authors address the practicalities of how data should be presented, summarized, and interpreted. There are no exact rules; indeed there are valid concerns that exact rules may be inappropriate and too prescriptive. New procedures evolve, and new methods may be needed to deal with new types of data, just as people know that new…

Online professional development (OPD) has potential to improve teacher quality by improving teachers' knowledge and instructional practices. These changes, in turn, have potential to improve student achievement. Unfortunately, there is a dearth of scientific research on the effects of OPD on teachers and, more importantly, on students. This…

This report summarizes the complex research literature on quantitative methods for assessing how impacts of educational interventions on instructional practices and student learning differ across students, educators, and schools. It also provides technical guidance about the use and interpretation of these methods. The research topics addressed…

Among his many accomplishments in educational psychology, Merlin C. Wittrock is perhaps best remembered for his enduring contributions to the science of learning. His vision of how learning works is best explicated in articles published in "Educational Psychologist" (Wittrock, 1974, 1978, 1989, 1991, 1992), beginning with his classic 1974 article,…

Through a synthesis of test publisher norms and national longitudinal datasets, this study provides new national norms of academic growth in K-12 reading and math that can be used to reinterpret conventional effect sizes in time units. We propose d' a time-indexed effect size metric to estimate how long it would take for an "untreated"…

During the 2009-2010 school year, Marzano Research Laboratory (MRL) was commissioned by Promethean Ltd. to conduct a second year evaluation study of the effects of Promethean ActivClassroom on student academic achievement. This executive summary highlights the key findings. [For "A Second Year Evaluation Study of Promethean ActivClassroom. Final…

Standardized effect sizes and confidence intervals thereof are extremely useful devices for comparing results across different studies using scales with incommensurable units. However, exact confidence intervals for standardized effect sizes can usually be obtained only via iterative estimation procedures. The present article summarizes several…

To provide an overview of the specific components that must be considered when making decisions about research in the field of gifted education, the authors describe and evaluate the three types of evidence--speculative or anecdotal, theoretical, and empirical--commonly offered in the literature of the field. Empirical, or evidence-based, research…