Proposed changes [Two-Stage / GS Designs]

posted by Helmut Homepage – Vienna, Austria, 2020-02-17 14:16 2a02:8388:6bc2:ce80:856f:1d4e:74d9:7171 – Posting: # 21178
Views: 1,561

Hi Mauricio,

» Instead of: "Type I error must be preserved and adjusted, and to demonstrate bioequivalence the level of confidence is 94.12%;"
»
» I will only propose that: It must be demonstrated that the type I error of the study is controlled.

OK in principle. It’s always a good idea not only to propose a change but give a justification. Maybe refer to the EMA’s and the WHO’s guidelines stating that the adjusted α has to be specified in the protocol and the choice is at the company’s discretion. α 0.0294 (i.e., the 94.12% CI) is definitely not the only possible one.

» Instead of: "This second group must have at least 50% of the previous group"
»
» I will propose that: The number of participants in the second stage must be calculated based on the data extracted from the first stage. The calculation must be justified considering possible losses and / or dropouts observed in the first stage.

OK. Do me a favor: Use estimated/estimation instead of calculated/calculation. ;-)
Of course, n2 is always based on the eligible subjects in the interim (n1), not on the subjects randomized.
Justification: A minimum stage 2 sample size is not covered by the published methods; any minimum n2 might inflate the Type I Error. If that sounds too statistical write “the patient’s risk” instead.

Cheers,
Helmut Schütz
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