# R-program for Supplementary Exercise 7.127 of IPS7e

library(pwr) 
d <- 350/650 # d= effect size= difference in means divided by standard deviation
pwr.t.test( d=d, n=75, sig.level=0.05, type="two.sample", alternative="two.sided")
pwr.t.test( d=d, n=75, sig.level=0.05, type="two.sample", alternative="greater")