Bioequivalence and Bioavailability Forum • Nonbinding futility rule

Nonbinding futility rule [Two-Stage / GS Designs]

posted by Ben – 2018-06-15 19:58 (2135 d 14:50 ago) – Posting: # 18908
Views: 15,123

Dear Detlew,

❝ My first thought was: Set fCpower = 1, that results in do not use the power futility criterion. This gives n2=16 for mittyri's example

❝ interim.tsd.in(GMR1=0.89, CV1=0.2575165, n1=38, fCpower=1).

❝

❝ Your suggestion

❝ interim.tsd.in(GMR1=0.89, CV1=0.2575165, n1=38, ssr.conditional = "error")

❝ gives also n2=16. Astonishing or correct?

This is correct. Please note that if fCpower = 1, then (as intended) the futility criterion regarding power of stage 1 never applies. If you then encounter a scenario where power of stage 1 is greater than targetpower (this must not happen, but it can happen), then the conditional estimated target power will be negative. Thus, we would have a problem with this being the target power for sample size calculation. To avoid this from happening the function automatically sets the target power for recalculation to targetpower (which is equivalent to ssr.conditional = "error"). See 'Details' in the man page.

❝ Avoiding the conditional sample size re-estimation, i.e. using the conventional sample size re-estimation via

❝ interim.tsd.in(GMR1=0.89, CV1=0.2575165, n1=38, ssr.conditional = "no")

❝ gives n2=4. Ooops? Wow!

I have to think about that :confused:

❝ IIRC the term "nonbinding" in the context of sequential designs is used for flexibility in stopping or continuing due to external reasons. Do we have such here?

For example?

❝ Binding, nonbinding - does it have an impact on the alpha control? I think not, but are not totally sure.

Non-binding: Type 1 error is protected, even if the futility criterion is ignored.
Binding: Type 1 error is protected only if the futility criterion will be adhered to. ('Binding' is not common practice, authorities don't want this).

Best regards,
Ben.

Complete thread:

Finally: Exact TSD methods for 2×2 crossover designs Helmut 2018-04-21 17:17
- 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 ruleBen 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