Nothing
epi.ssninfb <- function(treat, control, delta, n, power, r = 1, nfractional = FALSE, alpha){
# Stop if a negative value for delta entered:
if (delta < 0){
stop("For a non-inferiority trial delta must be greater than or equal to zero.")
}
z.alpha <- qnorm(1 - alpha, mean = 0, sd = 1)
if (!is.na(treat) & !is.na(control) & !is.na(delta) & !is.na(power) & is.na(n)) {
beta <- 1 - power
z.beta <- qnorm(1 - beta, mean = 0, sd = 1)
# delta equals the max absolute tolerable difference between treat and control.
# Make delta negative:
ndelta <- -delta
# Aniko Szabo 230821: Add check for non-existent solution:
if (sign(z.alpha + z.beta) != sign(treat - control - ndelta)){
stop("Target power is not reachable. Check the exact specification of the hypotheses.")
}
# http://powerandsamplesize.com/Calculators/Compare-2-Proportions/2-Sample-Non-Inferiority-or-Superiority:
if(nfractional == FALSE){
n.control <- ceiling((treat * (1 - treat) / r + control * (1 - control)) * ((z.alpha + z.beta) / (treat - control - ndelta))^2)
n.treat <- n.control * r
n.total <- n.treat + n.control
}
if(nfractional == TRUE){
n.control <- (treat * (1 - treat) / r + control * (1 - control)) * ((z.alpha + z.beta) / (treat - control - ndelta))^2
n.treat <- n.control * r
n.total <- n.treat + n.control
}
rval <- list(n.total = n.total, n.treat = n.treat, n.control = n.control, delta = delta, power = power)
}
if (!is.na(treat) & !is.na(control) & !is.na(delta) & !is.na(n) & is.na(power) & !is.na(r) & !is.na(alpha)) {
# delta equals the max absolute tolerable difference between treat and control.
# Make delta negative:
ndelta <- -delta
# Work out the number of subjects in the control group. r equals the number in the treatment group divided by the number in the control group.
if(nfractional == FALSE){
n.control <- ceiling(1 / (r + 1) * (n))
n.treat <- n - n.control
n.total <- n.treat + n.control
}
if(nfractional == TRUE){
n.control <- 1 / (r + 1) * (n)
n.treat <- n - n.control
n.total <- n.treat + n.control
}
# Replaced 010518 in response to email from Aline Guttmann on 080318:
z <- (treat - control - ndelta) / sqrt(treat * (1 - treat) / n.treat + control * (1 - control) / n.control)
# Original code:
# z <- (treat - control - ndelta) / sqrt(treat * (1 - treat) / n.treat / r + control * (1 - control) / n.control)
# Aniko Szabo 230821 - use only one tail:
power <- pnorm(z - z.alpha, mean = 0, sd = 1)
# Original code:
# power <- pnorm(z - z.alpha, mean = 0, sd = 1) + pnorm(-z - z.alpha, mean = 0, sd = 1)
rval <- list(n.total = n.total, n.treat = n.treat, n.control = n.control, delta = delta, power = power)
}
rval
}
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