Bioequivalence and Bioavailability Forum

Oops! [Two-Stage / GS Designs]

posted by d_labes  – Berlin, Germany, 2011-02-07 17:29 (5249 d 05:19 ago) – Posting: # 6569
Views: 27,020

Dear Helmut,

❝ good question, next question!

It was the best question I had at moment . But may be later on I have some better.

❝ ... No idea how Potvin et al. got their values.

According to their formula given in paragraph 2.3 they use the approximation via central shifted Student's t-distribution, shortly described in the accompanying material of package PowerTOST.
Check it via the undocumented and hidden function
.approx2.power.TOST(alpha=0.05, se=sqrt(0.020977), diffm=log(0.95),
                    ltheta1=log(0.8),ltheta2=log(1.25), n=12, df=10, bk=2)
>[1] 0.8412397
.approx2.power.TOST(alpha=0.0294, se=sqrt(0.020977), diffm=log(0.95),
                    ltheta1=log(0.8),ltheta2=log(1.25), n=12, df=10, bk=2)
>[1] 0.7561472

But what you discuss was not my point, I think. Or was your first sentence already the answer?
I need to know the power of Potvin B/C if I assume 'true' GMR=1.08, 'true' CV = 0.3 for instance. What to do with the steps in the decision scheme

• Check the power using an alpha ...
  
• calculate sample size using an alpha ...

which were done in Potvin et.al. with GMR=0.95?
Stay with 0.95 or replace with 1.08?

Complete thread:

• Potvin method B subtleties d_labes 2011-01-31 14:24 
  • Potvin method B subtleties jdetlor 2011-02-01 17:17
    • Potvin method B subtleties d_labes 2011-02-02 09:15
      • Potvin method B subtleties jdetlor 2011-02-02 16:08
        • Gould d_labes 2011-02-02 16:25
          • Gould jdetlor 2011-02-02 17:02
  • Another one ... d_labes 2011-02-07 14:32
    • Oops! Helmut 2011-02-07 15:24
      • Oops!d_labes 2011-02-07 16:29
        • Oops! Helmut 2011-02-07 16:47
          • Oops! ElMaestro 2011-02-07 17:06
            • Oops! Helmut 2011-02-07 17:17
              • Oops! ElMaestro 2011-02-07 18:35
          • Simul'ants in my pants d_labes 2011-02-08 09:07
            • Need for speed... ElMaestro 2011-02-13 10:57
              • Need for speed... d_labes 2011-02-15 14:06
                • Need for speed... ElMaestro 2011-02-15 17:39
                  • Pocock alpha's d_labes 2011-02-16 09:18
                    • ElMaestro's brain ElMaestro 2011-02-16 09:32
                      • ElMaestro's brain d_labes 2011-02-16 10:05
                        • ElMaestro's brain ElMaestro 2011-02-16 12:07
                          • Numbers d_labes 2011-02-16 13:45
  • Bonus counter-question ElMaestro 2011-02-07 23:44
    • Speed is the question d_labes 2011-02-08 08:36
  • New paper (method D for PE 0.90) Helmut 2011-04-18 12:58
    • New paper (method D for PE 0.90) d_labes 2011-04-19 08:58
      • New paper (method D for PE 0.90) Helmut 2011-04-19 14:30
      • New paper (method D for PE 0.90) ElMaestro 2011-04-19 14:49
        • Stopping criterion # futility rule Helmut 2011-04-19 15:28