Assumptions… [Power / Sample Size]

posted by Rocco_M – Mexico, 2019-09-09 16:35 (409 d 06:55 ago) – Posting: # 20560
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Gracias and sorry for confusion. Here is what I think I am not getting. When you run a FIM, you do not have two populations. You have a treatment and (perhaps) a control. So if you have a geometric CV, say, CV1 calculated from that one treatment sample in the FIM. [It is not pooled variance, is it? There is only one sample] there and then use it to design a parallel follow-up, do you need to assume that the CV of the other arm, call it CV2, is equal to CV1, and then CVp = pooled(CV1,CV2) as input into sample size formula, eg, sampleNTOST?

Much apology if I am missing this point. I do not seem to understand what are the components of the pooled variance that go into the sample size computation.

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