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## Rick Chappell <> Asst. Professor, Depts. of Statistics and Human Oncology
## <> University of Wisconsin at Madison <> chappell@stat.wisc.edu
## (608) 263-5572 / 262-2733 <> take logs
samplesize.bin <- function(alpha, beta, pit, pic, rho=.5)
{
## alpha is the scalar ONE-SIDED test size, or two-sided size/2
## beta is a scalar or vector of powers
## pit is the hypothesized treatment probability of success
## pic is the hypothesized control probability of success
## returns required TOTAL sample size, using arcsin transformation
## rho is the proportion of the sample devoted to treated group (0 <rho < 1)
as <- function(x)
{
asin(sqrt(x))
}
invas <- function(x) {
(sin(x))**2
}
Zalpha <- qnorm(1-alpha)
Zbeta <- qnorm(beta)
n <- Zalpha + Zbeta
n <- n/(as(pit) - as(pic))
n <- (n**2)/(4*rho*(1-rho))
round(n+.5,0)
}
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