Bioequivalence and Bioavailability Forum

PowerTOST sample size FDA full replicate T/R ratio at 85% [🇷 for BE/BA]

posted by Shuanghe  – Spain, 2016-01-25 18:49 (3340 d 04:57 ago) – Posting: # 15852
Views: 19,744

Hi all,

I just noticed some strange result when I was making sample size plot for FDA full replicate BE using Detlew's famous PowerTOST.

My understanding was that, with T/R ratio fixed (e.g., 90%), when ISCV increase from, say, 10% to 100%, sample size will increase with the increasing ISCV and reach a peak at ISCV=30% then sample size will decrease due to widened BE criteria and after a certain point size will increase again due to high variability. This is true when I tried T/R ratio of 95% or 90%. For example, this plot.



However, when I was trying T/R ratio of 85% (I know, weird and problematic ratio assumption for BE. Don't ask why. Let's just say that I had to do it), the size peak reached at ISCV=27-28%, not at 30%. See this picture.




Why is that? Since all other assumptions are same (e.g., T/R ratio is still 85%), when ISCV increased from e.g., 28% to 29% and 30%, shouldn't we need more subjects as the BE criteria is not widened yet?

If my understanding is correct, then maybe it's a bug of the package? If I'm wrong, could anyone explain it in plain English ? Many thanks.

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Edit: Category changed. [Helmut]

Complete thread:

• PowerTOST sample size FDA full replicate T/R ratio at 85%Shuanghe 2016-01-25 17:49 [🇷 for BE/BA] 
  • PowerTOST sample size FDA full replicate T/R ratio at 85% d_labes 2016-01-26 12:05
    • PowerTOST sample size FDA full replicate T/R ratio at 85% Shuanghe 2016-01-26 12:55
      • PowerTOST sample size FDA full replicate T/R ratio at 85% d_labes 2016-01-26 14:07
      • maximum sample size at which CV? Helmut 2016-01-26 16:31
        • maximum sample size at which CV? nobody 2016-01-26 17:40
        • maximum sample size at which CV? d_labes 2016-01-27 08:41
          • maximum sample size at which CV? nobody 2016-01-27 09:08
            • OT: Stop - think -act d_labes 2016-01-27 09:31
        • maximum sample size at which CV? Shuanghe 2016-01-28 12:44
          • target power 90% Helmut 2016-01-28 13:49
            • PowerTOST update d_labes 2016-02-01 19:16
              • #1,000 Helmut 2016-02-01 21:49
                • OT: post #1,000 d_labes 2016-02-02 21:17
                • #1,000 ElMaestro 2016-02-03 16:32
                  • #1,000 Helmut 2016-02-03 16:50
                  • OT: #1,000 d_labes 2016-02-05 15:50
                    • OT: #1,000 ElMaestro 2016-02-05 17:02
                      • OT: #1,000 d_labes 2016-02-05 19:48
                        • OT: #1,000 ElMaestro 2016-02-06 15:45
                          • OT: #1,000 nobody 2016-02-07 09:50