Skip to main content
Journal cover image

Sample size calculations for the design of cluster randomized trials: A summary of methodology.

Publication ,  Journal Article
Gao, F; Earnest, A; Matchar, DB; Campbell, MJ; Machin, D
Published in: Contemp Clin Trials
May 2015

Cluster randomized trial designs are growing in popularity in, for example, cardiovascular medicine research and other clinical areas and parallel statistical developments concerned with the design and analysis of these trials have been stimulated. Nevertheless, reviews suggest that design issues associated with cluster randomized trials are often poorly appreciated and there remain inadequacies in, for example, describing how the trial size is determined and the associated results are presented. In this paper, our aim is to provide pragmatic guidance for researchers on the methods of calculating sample sizes. We focus attention on designs with the primary purpose of comparing two interventions with respect to continuous, binary, ordered categorical, incidence rate and time-to-event outcome variables. Issues of aggregate and non-aggregate cluster trials, adjustment for variation in cluster size and the effect size are detailed. The problem of establishing the anticipated magnitude of between- and within-cluster variation to enable planning values of the intra-cluster correlation coefficient and the coefficient of variation are also described. Illustrative examples of calculations of trial sizes for each endpoint type are included.

Duke Scholars

Published In

Contemp Clin Trials

DOI

EISSN

1559-2030

Publication Date

May 2015

Volume

42

Start / End Page

41 / 50

Location

United States

Related Subject Headings

  • Sample Size
  • Research Design
  • Randomized Controlled Trials as Topic
  • Public Health
  • Humans
  • Health Behavior
  • General Clinical Medicine
  • Community Health Services
  • 42 Health sciences
  • 32 Biomedical and clinical sciences
 

Citation

APA
Chicago
ICMJE
MLA
NLM
Gao, F., Earnest, A., Matchar, D. B., Campbell, M. J., & Machin, D. (2015). Sample size calculations for the design of cluster randomized trials: A summary of methodology. Contemp Clin Trials, 42, 41–50. https://doi.org/10.1016/j.cct.2015.02.011
Gao, Fei, Arul Earnest, David B. Matchar, Michael J. Campbell, and David Machin. “Sample size calculations for the design of cluster randomized trials: A summary of methodology.Contemp Clin Trials 42 (May 2015): 41–50. https://doi.org/10.1016/j.cct.2015.02.011.
Gao F, Earnest A, Matchar DB, Campbell MJ, Machin D. Sample size calculations for the design of cluster randomized trials: A summary of methodology. Contemp Clin Trials. 2015 May;42:41–50.
Gao, Fei, et al. “Sample size calculations for the design of cluster randomized trials: A summary of methodology.Contemp Clin Trials, vol. 42, May 2015, pp. 41–50. Pubmed, doi:10.1016/j.cct.2015.02.011.
Gao F, Earnest A, Matchar DB, Campbell MJ, Machin D. Sample size calculations for the design of cluster randomized trials: A summary of methodology. Contemp Clin Trials. 2015 May;42:41–50.
Journal cover image

Published In

Contemp Clin Trials

DOI

EISSN

1559-2030

Publication Date

May 2015

Volume

42

Start / End Page

41 / 50

Location

United States

Related Subject Headings

  • Sample Size
  • Research Design
  • Randomized Controlled Trials as Topic
  • Public Health
  • Humans
  • Health Behavior
  • General Clinical Medicine
  • Community Health Services
  • 42 Health sciences
  • 32 Biomedical and clinical sciences