The safer choices project: Methodological issues in school-based health promotion intervention research

Randomized trials of school-based health promotion programs present unique design and analytical issues not widely discussed in the research literature. This article describes the Safer Choices study - a school-based program for prevention of HIV, other sexually transmitted diseases, and pregnancy - to illustrate critical methodological issues involved in large-scale, school-based intervention trials, particularly those evaluating interventions with a school-wide focus. The issues presented are: I) comparability of the intervention and control groups even when few units are randomized; 2) factors that affect the decision to use a cohort or cross-sectional design; and 3) appropriate analysis strategy when the unit of randomization and intervention is at the school level, bur observations are at the student level.