mHP.btilde | R Documentation |
The futility boundary btilde is computed by solving (under the alternative)
mHP.btilde(beta, cov.J)
beta |
the type II error |
cov.J |
the 3 x 3 covariance matrix |
P(\tilde{Z}_J^1≤\tilde{b} or \tilde{Z}_J^2≤\tilde{b}) = εβ
where the superscripts denote the stage and ε is the fraction of the type I error (α) spent and β is the type II error. We make use of the joint normal density of Z_{J} (the overall group) at each of the three stages and the fact that the \tilde{Z_J} is merely a translation of Z_J. So here the calculation is based on a mean of zero and has to be translated during use!
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