mHP.btilde {ASSISTant} | R Documentation |
The futility boundary \tilde{b}
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\le\tilde{b} or \tilde{Z}_J^2\le\tilde{b}) = \epsilon\beta
where the superscripts denote the stage and \epsilon
is the
fraction of the type I error (\alpha
) spent and \beta
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!