A Small Sample Randomized Clinical Trial Methodology Using N-of-1 Designs and Mixed Model Analysis

Background/Objectives: To date, research on substance abuse prevention relied extensively on large sample randomized clinical trials to evaluate intervention programs. These designs are appropriate for certain types of randomized prevention trials (e.g., efficacy or effectiveness for broad populations) but are unfeasible for other prevention science scenarios (e.g., rare pathologies, pilot studies, or replication tests at specific locales). Methods: An alternative randomized clinical trial is described that relies on much smaller samples, less resources than the large sample designs, randomization, N-of-1 designs for the intervention group, and mixed model analysis. Results: This methodology is illustrated using a small sample prevention study, which demonstrates its statistical power, flexibility, and sophistication for experimental testing of prevention-oriented research questions. Scientific Significance: This methodology can be applied to many existing prevention datasets to facilitate secondary analyses of existing datasets as well as novel studies. It is hoped that such efforts will include further development of the small sample design in substance abuse prevention contexts.