= Power for equal samples t test in R = For a __two-tailed__ test with type I error, alpha, with samples each of size, n, with means and standard deviations we compute the power. [COPY AND PASTE THE BELOW INTO R] {{{ fn <- function (alpha,mean1,mean2,sd1,sd2,n) { mdiff <- mean1 - mean2 pow <- 1 - pt(abs(qt(alpha/2, 2*n-2)), 2*n-2, mdiff/sqrt((sd1*sd1)/n+(sd2*sd2)/n)) cat("Power for (two-tailed) unequal sized groups unpaired t-test =") print(pow) } }}} [TYPE INTO R THE DESIRED INPUTS]. {{{ alpha <- 0.05 mean1 <- 2 mean2 <- 0 sd1 <- 4 sd2 <- 5 n <- 45 }}} AND RUN {{{ fn(alpha,mean1,mean2,sd1,sd2,n) }}}