In the "individually randomized group treatment" (IRGT) experimental design, individuals are first randomly assigned to a treatment arm or a control arm, but then within each arm, are grouped together (e.g., within classrooms/schools, through shared case managers, in group therapy sessions, through shared doctors, etc.) to receive…

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…

We investigated methods of including covariates in two-level models for cluster randomized trials to increase power to detect the treatment effect. We compared multilevel models that included either an observed cluster mean or a latent cluster mean as a covariate, as well as the effect of including Level 1 deviation scores in the model. A Monte…

Randomized controlled trials (RCTs) are considered the "gold standard" for evaluating an intervention's effectiveness. Recently, the federal government has placed increased emphasis on the use of opportunistic experiments. A key criterion for conducting opportunistic experiments, however, is that there is relatively easy access to data…

As a result of the 1998 reauthorization of Head Start, the Department of Health and Human Services conducted a national evaluation of the Head Start program. The goal of Head Start is to improve the school readiness skills of low-income children in the United States. There is a substantial body of experimental and correlational research that has…