Any suggestion on calculating sample size for a superior RCT in R or SAS? I have used the 'pwr' package which gives me a different result from the one I got from an online calculator (Sample size calculator (riskcalc.org)).
my parameters are control- change in mean- 20+/- 5 treatment- change in mean- 15 +/- 5 drop out -20% power-0.9
Any suggestion would be appreciable.