The randomized control trial (RCT) is the primary experimental design in education research due to its strong internal validity for causal inference. However, in situations where RCTs are not feasible or ethical, quasi-experiments are alternatives to establish causal inference. This paper serves as an introduction to several quasi-experimental…

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…

An aspect of a study is considered a confounding factor if it is not possible to tell whether the difference in outcomes is due to the intervention, the confounding factor, or both. In What Works Clearinghouse (WWC) study reviews, certified reviewers look for a specific type of confounding factor: those that occur when a component of the study…

"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…

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…

Discipline-based education researchers have a natural laboratory--classrooms, programs, colleges, and universities. Studies that administer treatments to multiple sections, in multiple years, or at multiple institutions are particularly compelling for two reasons: first, the sample sizes increase, and second, the implementation of the treatments…

Randomized control trials are considered the gold standard for conducting research and estimating causal effects; however, educational research rarely lends itself to experimental design and true randomization. In recent years, there has been a growing interest in finding new approaches to estimate causal effects in nonrandomized studies in…

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…

The "Current Insights" feature is designed to introduce life science educators and researchers to current articles of interest in other social science and education journals. In this installment, I highlight three diverse research studies out of psychology journals that address student study strategies, faculty change, and the influence…

E-learning research is plenty of difficulties, as also research in education is. Usually, the high number of features involved in e-learning processes complicates and masks the identification and isolation of the factors which cause the expected benefits, when they exist. At the same time, a bunch of threats are ready to weaken the validity 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…

University-school collaboration can extend past the notion of simple shared resources in order to connect ideas, share talents, and solve problems mutually. It also provides fertile ground for counseling researchers to obtain, analyze and disseminate data. University-school collaborations signify a connective relationship between two vital and…

This Methodological Brief introduces the reader to the regression discontinuity design (RDD), which is a method that when used correctly can yield estimates of research treatment effects that are equivalent to those obtained through randomized control trials and can therefore be used to infer causality. However, RDD does not require the random…

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…

Given scarce resources for evaluation, we recommend that education researchers more frequently conduct comprehensive randomized trials that generate evidence on how, why, and under what conditions interventions succeed or fail in producing effects. Recent experience evaluating a randomized need-based financial aid intervention highlights some of…