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.…

PCI Education sought scientifically based evidence on the effectiveness of the "PCI Reading Program--Level One" for students with severe disabilities. During the 2007-2008 academic year. Empirical Education conducted a randomized control trial (RCT) in two Florida districts, Brevard and Miami-Dade County Public Schools. For this…