Efficient designs: factorial randomized trials.

Abstract

As an alternative to conducting multiple parallel group randomized controlled trials, the factorial design is an efficient means of evaluating multiple interventions. This review highlights when it is appropriate to conduct a factorial trial, considers the structure and nomenclature of factorial designs, and discusses various methodological considerations, including sample size calculation, the role of statistical interactions between different interventions, and statistical power. Several pertinent examples in orthopaedics and medicine are used to highlight the key concepts.