Bioequivalence and Bioavailability Forum • “classical” GSD

“classical” GSD - E[n] [Two-Stage / GS Designs]

posted by d_labes – Berlin, Germany, 2015-11-30 12:15 (3062 d 14:53 ago) – Posting: # 15684
Views: 12,400

Dear Helmut,

❝ Now my questions (especially @Ben). If the CV is lower than the ‘best guess’ in the GSD we have to go full throttle with another 50 subjects. Compare the column “2nd%” which gives the chance to proceed to the 2^nd part. Not only the chance is higher in the GSD, we are punished with another 50 subjects. Have a look at the TSD’s column “E[N]” giving the expected average total sample size. Much lower.

Much lower than what?
Your presentation of the GSD results is a little bit unfair. It seems that the expected N is 100.
But thats not true:

E[N] = (1-pctS2/100)*n1 + (pctS2/100)*(n1+n2)

in case of a GSD with one interim. That gives f.i. E[N] = 71.3 for CV=40% and n1=n2=50. IMHO not that much higher compared to 64 for the adaptive TSD.

The fact itselve is left: E[N]_GSD > E[N]_TSD, at least for this example.

—
Regards,

Detlew

Complete thread:

Adaptive TSD vs. “classical” GSD Helmut 2015-11-27 19:05
- Adaptive TSD vs. “classical” GSD ElMaestro 2015-11-27 19:54
- “classical” GSD - E[n]d_labes 2015-11-30 11:15
  - Apples are pears by comparing the weight Helmut 2015-12-01 16:35
    - Apples are pears by comparing the weight d_labes 2015-12-03 09:16
      - Apples are pears by comparing the weight Helmut 2015-12-03 13:10
        
        Oranges d_labes 2015-12-03 13:56
- Adaptive TSD vs. “classical” GSD Ben 2015-12-02 19:27
  - Adaptive TSD vs. “classical” GSD Helmut 2015-12-03 03:11
    - “classical” GSD alpha's d_labes 2015-12-03 09:47
      - N sufficiently large‽ Helmut 2015-12-03 14:56
        
        An other one with 0.0304 d_labes 2015-12-03 16:15
        
        An other one with 0.0304 Helmut 2015-12-03 16:26
    - Adaptive TSD vs. “classical” GSD Ben 2016-01-10 12:43