title: Imbalance properties of centre-stratified permuted-block and complete randomisation for several treatments in a clinical trial.
abstract: Randomisation schemes are rules that assign patients to treatments in a clinical trial. Many of these schemes have the common aim of maintaining balance in the numbers of patients across treatment groups. The properties of imbalance that have been investigated in the literature are based on two treatment groups. In this paper, their properties for K > 2 treatments are studied for two randomisation schemes: centre-stratified permuted-block and complete randomisation. For both randomisation schemes, analytical approaches are investigated assuming that the patient recruitment process follows a Poisson-gamma model. When the number of centres involved in a trial is large, the imbalance for both schemes is approximated by a multivariate normal distribution. The accuracy of the approximations is assessed by simulation. A test for treatment differences is also considered for normal responses, and numerical values for its power are presented for centre-stratified permuted-block randomisation. To speed up the calculations, a combined analytical/approximate approach is used. Copyright © 2016 John Wiley & Sons, Ltd.
authors.affiliation: School of Mathematics and Statistics, University of Glasgow, 15 University Gardens, Glasgow, G12 8QW, U.K.
authors.forename: Vladimir V
authors.initials: VV
authors.lastname: Anisimov
authors.affiliation: Roche Products Limited, 6 Falcon Way, Shire Park, Welwyn Garden City, AL7 1TW, U.K.
authors.forename: Wai Y
authors.initials: WY
authors.lastname: Yeung
authors.affiliation: School of Mathematical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS, U.K.
authors.forename: D Stephen
authors.initials: DS
authors.lastname: Coad
mesh_terms: D006801:Humans; D015233:Models, Statistical; D018579:Patient Selection; D016012:Poisson Distribution; D011897:Random Allocation; D016032:Randomized Controlled Trials as Topic / Q000379:methods; D013223:Statistics as Topic / Q000379:methods*
keywords: Poisson-gamma model; covariance; multicentre clinical trial; multivariate normal distribution; power; simulation