title: Best (but oft-forgotten) practices: designing, analyzing, and reporting cluster randomized controlled trials.
abstract: Cluster randomized controlled trials (cRCTs; also known as group randomized trials and community-randomized trials) are multilevel experiments in which units that are randomly assigned to experimental conditions are sets of grouped individuals, whereas outcomes are recorded at the individual level. In human cRCTs, clusters that are randomly assigned are typically families, classrooms, schools, worksites, or counties. With growing interest in community-based, public health, and policy interventions to reduce obesity or improve nutrition, the use of cRCTs has increased. Errors in the design, analysis, and interpretation of cRCTs are unfortunately all too common. This situation seems to stem in part from investigator confusion about how the unit of randomization affects causal inferences and the statistical procedures required for the valid estimation and testing of effects. In this article, we provide a brief introduction and overview of the importance of cRCTs and highlight and explain important considerations for the design, analysis, and reporting of cRCTs by using published examples.
authors.affiliation: Office of Energetics, Nutrition Obesity Research Center, and awbrown@uab.edu dallison@uab.edu.
authors.forename: Andrew W
authors.identifier: 0000-0002-1758-8205
authors.initials: AW
authors.lastname: Brown
authors.affiliation: Office of Energetics.
authors.forename: Peng
authors.initials: P
authors.lastname: Li
authors.affiliation: Department of Food, Nutrition, and Packaging Sciences, Clemson University, Clemson, SC;
authors.forename: Michelle M
authors.identifier: 0000-0002-7959-9225
authors.initials: MM
authors.lastname: Bohan Brown
authors.affiliation: Office of Energetics, Nutrition Obesity Research Center, and.
authors.forename: Kathryn A
authors.identifier: 0000-0002-6258-4369
authors.initials: KA
authors.lastname: Kaiser
authors.affiliation: Division of Biostatistics, Department of Pharmacology and Experimental Therapeutics, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA; and.
authors.forename: Scott W
authors.initials: SW
authors.lastname: Keith
authors.affiliation: Division of Epidemiology & Community Health, School of Public Health, University of Minnesota, Minneapolis, MN.
authors.forename: J Michael
authors.initials: JM
authors.lastname: Oakes
authors.affiliation: Office of Energetics, Nutrition Obesity Research Center, and Department of Biostatistics, University of Alabama at Birmingham, Birmingham, AL; awbrown@uab.edu dallison@uab.edu.
authors.forename: David B
authors.initials: DB
authors.lastname: Allison
mesh_terms: D016000:Cluster Analysis; D006801:Humans; D052756:Nutritional Sciences / Q000379:methods* / Q000639:trends; D010506:Periodicals as Topic; D017410:Practice Guidelines as Topic; D011643:Publishing / Q000592:standards / Q000639:trends; D016032:Randomized Controlled Trials as Topic / Q000379:methods* / Q000592:standards / Q000639:trends; D012107:Research Design / Q000592:standards / Q000639:trends; D013223:Statistics as Topic / Q000379:methods* / Q000592:standards / Q000639:trends
keywords: community randomized trial; group randomized trial; intraclass correlation coefficient; power analysis; reporting fidelity