• Linda M Collins, John J Dziak, Kari C Kugler, and Jessica B Trail.
• Department of Human Development and Family Studies; The Methodology Center. Electronic address: lmcollins@psu.edu.
• Am J Prev Med. 2014 Oct 1; 47 (4): 498-504.

BackgroundAn understanding of the individual and combined effects of a set of intervention components is important for moving the science of preventive medicine interventions forward. This understanding can often be achieved in an efficient and economical way via a factorial experiment, in which two or more independent variables are manipulated. The factorial experiment is a complement to the RCT; the two designs address different research questions.PurposeTo offer an introduction to factorial experiments aimed at investigators trained primarily in the RCT.MethodsThe factorial experiment is compared and contrasted with other experimental designs used commonly in intervention science to highlight where each is most efficient and appropriate.ResultsSeveral points are made: factorial experiments make very efficient use of experimental subjects when the data are properly analyzed; a factorial experiment can have excellent statistical power even if it has relatively few subjects per experimental condition; and when conducting research to select components for inclusion in a multicomponent intervention, interactions should be studied rather than avoided.ConclusionsInvestigators in preventive medicine and related areas should begin considering factorial experiments alongside other approaches. Experimental designs should be chosen from a resource management perspective, which states that the best experimental design is the one that provides the greatest scientific benefit without exceeding available resources.Copyright © 2014 American Journal of Preventive Medicine. Published by Elsevier Inc. All rights reserved.

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