But what is the real problem? [Two-Stage / GS Designs]

posted by Mikalai  – Belarus, 2018-06-07 15:47  – Posting: # 18865
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Good afternoon everyone
I just would like to clarify a bit the situation. We have a drug and do not know it CV. We take an arbitrary sample and then calculate the CV and real GMR in the first stage. In the second stage, we, if I understand correctly, should calculate post-hoc power and recalculate the sample size with the data (GMR and CV) obtained in the first stage, if bioequivalence has not been achieved in the first stage. But what to do, if we have got bad GMR(0,83), whatever CV and low power (around 30) in the first stage. In this case, as I understand, we should recruit much more subjects according to our protocol. The questions, how can we avoid slipping into "forced bioequivalence"? Or should we go straight away and recruit this large number of subjects? What should be put into the protocol?
Best regards,
Mikalai

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