Field experiments with nested structures are becoming increasingly common, especially designs that assign randomly entire clusters such as schools to a treatment and a control group. In such large-scale cluster randomized studies the challenge is to obtain sufficient power of the test of the treatment effect. The objective is to maximize power…

This is an application of contemporary multilevel regression modeling to the prediction of academic performances of 1st-year college students. At a first level of analysis, the data come from N greater than 16,000 students who were college freshman in 1994-1995 and who were also participants in high-level college athletics. At a second level of…

Analysis of multivariate aptitude-treatment-interaction data is discussed. Analysis procedures are illustrated using data from a science education study to describe the interaction between student reading ability and the time allowed in an individualized instructional approach for multiple achievement and attitudinal outcomes. (Author/RL)