Bioequivalence and Bioavailability Forum

Selection of w and w* [Two-Stage / GS Designs]

posted by Helmut  – Vienna, Austria, 2018-04-26 11:51 (2189 d 02:48 ago) – Posting: # 18733
Views: 16,133

Dear Detlew,

❝ Defining the weights that way is IMHO not what you intended.

OK, I see!

❝ BTW: Choosing the weights "optimal" is for me a mystery. To do that, we had to know the outcomes of the two stages, but we don't have them until the study has been done. On the other hand we have to predefine them to gain strict TIE control. Hier beißt sich die Katze in den Schwanz.

Using the median of n.tot to define the weights from the sim’s was a – maybe too naïve – attempt. Other suggestions? Some regulatory statisticians prefer the first stage in a TSD to be like in a fixed sample design. For some combinations of n₁/CV in my grid this will be ≤ the median of n.tot. In other words, I’m not too optimistic but rather too pessimistic. Now what?
Example: CV 0.1, GMR 0.95, target power 0.80. Fixed sample design’s n 8 (n₁ ⇒ 12 acc. to GLs). n.mean and median of n.tot 12 with the default weights (0.5, 0.25). Even the 95% percentile of n.tot is 12.

—
Dif-tor heh smusma 🖖🏼 Довге життя Україна! 
Helmut Schütz


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Science Quotes

Complete thread:

• Finally: Exact TSD methods for 2×2 crossover designs Helmut 2018-04-21 17:17 [Two-Stage / GS Designs] 
  • Exact TSD methods: Example Helmut 2018-04-21 20:33
  • Finally: Exact TSD methods for 2×2 crossover designs ElMaestro 2018-04-21 20:49
    • Flow chart (without details) Helmut 2018-04-21 21:41
      • naive questions regarding new functions in Power2Stage mittyri 2018-04-28 15:54
        • Some answers Helmut 2018-04-28 17:29
        • Some more "answers" d_labes 2018-04-29 21:11
          • clarification regarding user Power2Stage guides mittyri 2018-04-30 13:41
  • Technicality: Weigths for the inverse normal approach d_labes 2018-04-25 14:19
    • Selection of w and w*Helmut 2018-04-26 09:51
      • Selection of w and w* d_labes 2018-04-26 20:02
      • Now what? w & w* examples d_labes 2018-05-09 13:53
        • Now what? w & w* examples Ben 2018-06-10 20:12
          • Now what? w & w* examples Helmut 2018-06-11 13:57
            • Now what? w & w* examples Ben 2018-06-12 19:14
          • a bug in interim.tsd.in()? mittyri 2018-06-11 23:27
            • a bug in interim.tsd.in()? Ben 2018-06-12 19:32
              • Nonbinding futility rule d_labes 2018-06-13 16:59
                • Bad weather? Helmut 2018-06-13 19:23
                  • NLYW? d_labes 2018-06-14 10:18
                • Nonbinding futility rule Ben 2018-06-13 20:26
                  • Nonbinding futility rule d_labes 2018-06-14 10:47
                    • Nonbinding futility rule Ben 2018-06-15 17:58
                      • Binding / Nonbinding futility rule - alpha control d_labes 2018-06-16 19:42
                        • Binding / Nonbinding futility rule - alpha control Ben 2019-03-30 09:52