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Hi, I try to calculate the sample size for the following design: - endpoint: response rate - response rate placebo: 15% - relative risk: 3 - 9 arms; 8 arms with Novum are compared versus Placebo - alpha(overall): 5% - Power: 80% - it is sufficient, if 1 arm is better than placebo My sample size program allows only 2 arms, so I made a Sidak alpha correction (for the 8 comparisons), so alpha goes down from 5% to 0.639%. I come up with n=60 patients per arm. The problem now is: using a simulation I realized that the power increased to 98%. So do I have to make the Sidak correction as well for the power? I tried this with my simulation but this seems not to work (if I use a Sidak corrected power of 18.2%, I get n=17 per arm, but with this my simulation shows less than 40% power). Any help is appreciated, as well literature recommendation. Thanks, Chr. You may leave the list at any time by sending the command SIGNOFF allstat to [log in to unmask], leaving the subject line blank.