Sample size calculations for the design of cluster randomized trials: A summary of methodology.
Abstract
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.
Type
Journal articleSubject
HumansSample Size
Health Behavior
Research Design
Community Health Services
Randomized Controlled Trials as Topic
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https://hdl.handle.net/10161/22873Published Version (Please cite this version)
10.1016/j.cct.2015.02.011Publication Info
Gao, Fei; Earnest, Arul; Matchar, David B; Campbell, Michael J; & Machin, David (2015). Sample size calculations for the design of cluster randomized trials: A summary of
methodology. Contemporary clinical trials, 42. pp. 41-50. 10.1016/j.cct.2015.02.011. Retrieved from https://hdl.handle.net/10161/22873.This is constructed from limited available data and may be imprecise. To cite this
article, please review & use the official citation provided by the journal.
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Show full item recordScholars@Duke
David Bruce Matchar
Professor of Medicine
My research relates to clinical practice improvement - from the development of clinical
policies to their implementation in real world clinical settings. Most recently my
major content focus has been cerebrovascular disease. Other major clinical areas in
which I work include the range of disabling neurological conditions, cardiovascular
disease, and cancer prevention. Notable features of my work are: (1) reliance on
analytic strategies such as meta-analysis, simulation, decision analy

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