Experiments that assign intact groups to treatment conditions are increasingly common in social research. In educational research, the groups assigned are often schools. The design of group randomized experiments requires knowledge of the intraclass correlation structure to compute statistical power and sample sizes required to achieve adequate power. This paper provides a compilation of intraclass correlation values of academic achievement and related covariate effects that could be used for planning group randomized experiments in education. It also provides variance component information that is useful in planning experiments involving covariates, and illustrates the use of these values to compute statistical power of group randomized experiments.
In this essay, Vivian Tseng and the William T. Grant Foundation senior program team describe the Foundation's interest in generating studies that focus on understanding the use of research evidence in policy and practice affecting youth and how to improve its use. The authors begin by defining what the Foundation means by research evidence and use of research evidence, acknowledging that research evidence is only one of several forms of evidence important to policymakers and practitioners. Tseng and colleagues then discuss reasons for studying the use of research evidence, and offer some early thoughts about fertile ground for future studies.