The What Works Clearinghouse (WWC) has updated its 2009 intervention report for SuccessMaker®, a set of computer-based courses designed to supplement regular K-8 reading instruction. The program is designed to improve skills in areas such as concepts of print, phonological awareness, phonics, fluency, vocabulary, comprehension, grammar, and…

Randomized experiments are often considered the strongest designs to study the impact of educational interventions. Perhaps the most prevalent class of designs used in large scale education experiments is the cluster randomized design in which entire schools are assigned to treatments. In cluster randomized trials (CRTs) that assign schools to…

Background: Cluster-randomized experiments that assign intact groups such as schools or school districts to treatment conditions are increasingly common in educational research. Such experiments are inherently multilevel designs whose sensitivity (statistical power and precision of estimates) depends on the variance decomposition across levels.…