RE: population size and confidence power

From: "Kowalski, Ken" Ken.Kowalski@pfizer.com Subject: RE: [NMusers] population size and confidence power Date: Mon, April 4, 2005 5:04 pm Lin Lin, To add to Nick's comments regarding the various quantities that need to be specified, for the hypothesis testing procedure (Nick's item 3 below) we must also specify the type I error rate (alpha). To this end, it is good practice to perform simulations under the null hypothesis of no effect and show that we only reject the null hypothesis alpha percent ( e.g., 5% if alpha=0.05) of the time. This is important as different estimation methods may perform differently regarding maintaining the type I error rate (see papers by Wahlby et al in JPP 2001;28:231-252 and JPP 2002;29:251-269). Inflated type I errors are likely to result in inflated estimates of power when using the test assuming that the type I error rate is maintained. Ken _______________________________________________________