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Balance in cluster randomised trials.

Raab, Gillian; Butcher, Izzy

Authors

Gillian Raab

Izzy Butcher



Abstract

This paper explores the role of balancing covariates between treatment groups in the design of cluster randomized trials. General expressions are obtained for two criteria to evaluate designs for parallel group studies with two treatments. The first is the variance of the estimated treatment effect and the second is the extent to which the estimated treatment effect is changed by adjusting for covariates. It is argued that the second of these is more important for cluster randomized trials. Methods of obtaining balanced designs from covariates which are available at the start of a study are proposed. An imbalance measure is used to compare the extent to which designs balance important covariates between the arms of a trial. Several approaches to selecting a well balanced design are possible. A method that randomly selects one member from the class of designs with acceptable bias will allow randomization inference as well as model-based inference. The methods are illustrated with data from a trial of school-based sex education.

Citation

Raab, G., & Butcher, I. (2001). Balance in cluster randomised trials. Statistics in Medicine, 20, 351-365. https://doi.org/10.1002/1097-0258%2820010215%2920%3A33.0.CO%3B2-C

Journal Article Type Article
Publication Date Feb 15, 2001
Deposit Date May 2, 2008
Print ISSN 0277-6715
Electronic ISSN 1097-0258
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 20
Pages 351-365
DOI https://doi.org/10.1002/1097-0258%2820010215%2920%3A33.0.CO%3B2-C
Keywords Covariates; Cluster randomized trials; Estimated treatment effect; Imbalance measure
Public URL http://researchrepository.napier.ac.uk/id/eprint/1607
Publisher URL http://www3.interscience.wiley.com/journal/76509002/abstract

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