Achieve3000 publishes a number of online literacy programs that differentiate lessons and activities based on student performance. Magnolia Consulting--an independent, third party evaluation firm--assessed Achieve3000 Solutions' impact on student learning during the 2014-15 school year. The researchers used a randomized control trial, where…

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.…