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SUMMARY:Sample size calculations for cluster randomised trials - Eldridge\
 , S (QMUL)
DTSTART:20110815T142500Z
DTEND:20110815T150500Z
UID:TALK32357@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:In this talk I will address the major issues in calculating an
  adequate sample size for cluster randomised trials. It has long been reco
 gnised that in order for these trials to be adequately powered\, between c
 luster variability must be accounted for in the sample size calculations. 
 This is usually done by using an estimate of the intra-cluster correlation
  coefficient (ICC) in a design effect which is then used to adjust the sam
 ple size required for an individually randomised trial aiming to detect th
 e same clinically important difference. More recently it has been recognis
 ed that variable cluster size should also be accounted for and a simple ad
 justment to the design effect provides a means to do this. Investigators s
 till face three challenges\, however: lack of information about variabilit
 y in cluster size prior to the trial\, lack of information about the value
  of the ICC prior to the trial\, the adjustment for variable cluster size 
 does not strictly match all methods of analysis. I will illustrate these c
 hallenges with some examples and outline approaches that have been and cou
 ld be adopted to address them.\n
LOCATION:Seminar Room 1\, Newton Institute
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