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An investigator hypothesizes that the improvement rate associated with a placebo is P1 = 0.45, and that the improvement rate associated with an active drug is P2 = 0.65. The plan is to perform a two-tailed test. Use SAS to complete each problem below. (a) If a significance level 0.01 and a power of 0.95 are desired, how large a sample per treatment must he study? (b) How large must the sample size be if the significance level is relaxed to 0.05 and the power to 0.85? (c) For this study, suppose that you have funds to recruit 130 patients per group. What is the power for a 5% level test for this sample size? First do the computation by hand and then use SAS to confirm.
An investigator hypothesizes that the improvement rate associated with a placebo is P1 = 0.45, and that the improvement rate associated with an active drug is P2 = 0.65. The plan is to perform a two-tailed test. Use SAS to complete each problem below.
(a) If a significance level 0.01 and a power of 0.95 are desired, how large a sample per treatment must he study?
(b) How large must the sample size be if the significance level is relaxed to 0.05 and the power to 0.85?
(c) For this study, suppose that you have funds to recruit 130 patients per group. What is the power for a 5% level test for this sample size? First do the computation by hand and then use SAS to confirm.