Objective: Sample size and statistical power calculation should consider clustering effects when schools are the unit of randomization in intervention studies. The objective of the current study was to investigate how student outcomes are clustered within schools in an obesity prevention trial. Method: Baseline data from the Food, Health &…

The "Morbidity and Mortality Weekly Report" ("MMWR") Series is prepared by the Centers for Disease Control and Prevention (CDC). Data in the weekly "MMWR" are provisional, based on weekly reports to CDC by state health departments. This issue of "MMWR" contains the following studies: (1) Youth Risk Behavior…