Based on cognitive load theory, the effect of different levels of instructional detail and expertise in a simulation-based environment on learning about concepts of correlation was investigated. Separate versions of the learning environment were designed for the four experimental conditions which differed only with regard to the levels of written…

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.…