Statistical Power in Three-Arm Cluster Randomized Trials. (December 2014)

• Record Type: Journal Article
• Authors: Liu, Xiaofeng Steven
• Is Part Of: Evaluation & the health professions. Volume 37:Number 4(2014:Dec.)
• Page Start: 470
• Page End: 487
• Publication Date: 2014-12
• Subjects: statistical power -- sample size -- cluster randomized trial; Medical care -- Evaluation -- Periodicals; Medicine -- Ability testing -- Periodicals; 362.105
• DOI: 10.1177/0163278713498392
• Languages: English
• ISSNs: 0163-2787

Abstract

This article shows how to compute statistical power for testing the main effect of treatment in three-arm cluster randomized trials. Using orthogonal coding, we derive the exact test statistic of the treatment effect and its non-central distribution. The non-centrality parameter in the omnibus test is found to be related to the non-centrality parameters in the contrast tests. A study of physician and pharmacist comanagement of patients' blood pressure is used as an example to show the power computation in a three-arm cluster randomized trial.