Bioequivalence and Bioavailability Forum • Need for speed...

Need for speed... [Two-Stage / GS Designs]

posted by ElMaestro – Denmark, 2011-02-15 18:39 (5196 d 21:55 ago) – Posting: # 6628
Views: 25,932

Ahoy d_labes,

❝ Of course :-D ! But remember my post to find out that the approximations work reasonable good for the decision power>=80% or power<80%. But if approximate I would go for the non-central t-distribution.

I think you are right about that.
I looked at the difference in power estimates in exactly that region of 80% and it comes down to decimals between the different methods.
However, I do not have an understanding of the way Potvin et al. derive their alpha values - if you could enlighten me I would really appreciate it.
I would imagine them to backcalculate alpha from the total simulated power using their power formula on pg 252, but at the moment my numbers do not fit. Example method B:
We know that at alpha=0.0294 at each stage, CV=0.3, and n1=36 power is found to be 0.8379 and in the simulations avgN=40.7. I cannot make those numbers fit the overall alpha of 0.0397 (within rounding boundaries).

❝ Do you think that your C-code can made interacting with R to facilitate such things as other methods for sample size adaption, other nominal alpha values for the two stages, introduction of a maximum number of subjects ...?

That would be a nice objective. Can't imagine it would be difficult as such to make it interact; I have previously written code that could shell-execute R and do whatever R script the C code asks for, including dumping R output to a textfile, but it takes a lot of time to write such code. It comes down to having the time to do it, I think.

—
Pass or fail!
ElMaestro

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