groupSampleSize  R Documentation 
In the three stage design under consideration, the groups are nested with assumed prevalences and fixed total sample size at each stage. This function returns the sample size for a specified group at a given stage, where the futility stage for the overall group test may be specified along with the chosen subgroup.
groupSampleSize( prevalence, N, stage, group, HJFutileAtStage = NA, chosenGroup = NA )
prevalence 
the vector of prevalence, will be normalized if not already so. The length of this vector implicitly indicates the number of groups J. 
N 
an integer vector of length 3 indicating total sample size at each of the three stages 
stage 
the stage of the trial 
group 
the group whose sample size is desired 
HJFutileAtStage 
is the stage at which overall futility
occured. Default 
chosenGroup 
the selected group if HJFutilityAtStage is not

the sample size for group
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