Analysis issues in school-based health promotion studies

In school-based research, usually the nature of the intervention or other practical factors indicate that assignment of treatment be done by school or classroom rather than by individual student. In this situation, randomization of schools (or classrooms) and analysis by school means (or classroom means) provide a firm statistical basis for internal validity of the study. When the number of schools available is small, this approach is not practicable, and therefore the investigator must be both more creative in developing solutions and more cautious in interpreting the results. This article provides a number of suggestions which the authors hope will assist the field in dealing with such circumstances. The authors stress that the best approach to assessing treatment effect is a well-designed, properly analyzed randomized experiment. The suggestions in this article attempt to indicate how one might make the most that one can from more limited data.