swh:1:snp:ff0951ca787d0b7f47dc2335f47fed43820a6324
Tip revision: f0140af03c815c42737db208e523a92d8cbf98a6 authored by Venkatraman E. Seshan on 09 April 2010, 00:00:00 UTC
version 0.8.9
version 0.8.9
Tip revision: f0140af
pselect.Rd
\name{pselect}
\title{Probability of selection under pick the winner rule}
\alias{pselect}
\keyword{design}
\description{
Calculates the probability of selecting the treatment with the higher
response rate under the pick the winner rule.
}
\usage{
pselect(n, p, min.diff=NULL, min.resp=NULL)
}
\arguments{
\item{n}{sample size for each treatment arm. This is either a single
integer or a vector of two integers for the special case of
comparing two treatments with unequal sample sizes}
\item{p}{vector of response rates for the treatments.}
\item{min.diff}{this is the number of responses or the rate by which
the best treatment should be superior to the others to be chosen.
This must be a positive integer or a rate between 0 and 1. If
missing it defaults to 1 for the equal sample size case but quits
with a warning for the unequal sample size case.}
\item{min.resp}{the minimum number of responses in each treatment arm
for it to be considered further. If missing defaults to 0.}
}
\value{
the function returns a list with:
\item{prob.none.worthy}{is the probability that no treatment has the
minimum number of responses specified in min.resp. this element is
present only if min.resp is greater than 0 for at least one arm.}
\item{prob.inconclusive}{this is the probability that the best treatment
has the requisite min.resp responses but exceeds the second best by
less than min.diff responses (rate) provided the second best also
has at least min.resp responses.}
\item{prob.selection}{this is a matrix which for each treatment gives
the response probability and the probability of selecting it
i.e. the number of responses in the chosen arm is at least min.resp
and either none of the remaining arms exceed the min.resp threshold
or the chosen (best) arm is better than the second best by at least
min.diff responses (rate).}
}
\examples{
pselect(18, c(0.2, 0.2, 0.2)) # selection when no diffrence i.e. type I error
pselect(18, c(0.2, 0.2, 0.4)) # selection probability
pselect(26, c(0.2, 0.2, 0.4), min.diff=2, min.resp=3)
pselect(c(27,54), c(0.5, 0.65), min.diff=0.05) # unequal sample size case
pselect(c(27,54), c(0.5, 0.65), min.diff=0.05, min.resp=c(14,27)) # unequal sample size case
}
\references{
Simon R, Wittes RE, Ellenberg SS. (1985). Randomized phase II clinical
trials. \emph{Cancer Treat Rep} 69, 1375-1381.
}