Bioequivalence and Bioavailability Forum • Initial sample size guess for the Potvin methods

Initial sample size guess for the Potvin methods [Two-Stage / GS Designs]

posted by ElMaestro – Belgium?, 2017-08-19 16:14 (1079 d 21:24 ago) – Posting: # 17711
Views: 24,734
(edited by ElMaestro on 2017-08-19 17:14)

Hi Hötzi,

»

Error in Power.calc(nps1, GMR, CV, Is.St2 = 1) :


»   could not find function "Power.calc"

» Did I specify the arguments wrongly?

That's why I included the remark:
##equation in Potvin et al.
I thought you'd be plugging in your own, but be that as it may.

An implementation of the function is here:

alpha1=0.0294

alpha2=0.05

vecQT1=c(1:5000)

vecQT2=c(1:5000)

for (i in 1:5000)

   {

    vecQT1[i]=qt(p=1-alpha1, df=i) 

    vecQT2[i]=qt(p=1-alpha2, df=i) 

   }







Power.calc=function(Nps, GMR, CV, Is.St2=0)

{

  s=sqrt(log(1+CV*CV))

  nom1=log(1.25/GMR)

  nom2=-log(1.25*GMR)

  den=s*sqrt(2/(2*Nps))

  df=Nps*2-2

  if (Is.St2==T) df=df-1

  ##cat("1-a=", 1-alpha, "df=",df,"\n")

  if (Is.St2==0) q=vecQT1[df]


    else         q=vecQT2[df]


  pw=pt( (nom1/den) -q, df) - pt( (nom2/den) +q, df)

  if (pw<0) pw=0.01

  return(pw)



}

Edit: Forgot to write: For classical B the alphas are (0.0294, 0.0294) and for C they are (0.05, 0.0294) though that isn't related to the topic. Second, Hötzi, you gave a little table which I am not very sure how to read. Note this isn't about the sample size calculation itself, this is about the initial guess used for the sample size calculation by up/down iteration.

—
I could be wrong, but...

Best regards,
ElMaestro

"Pass or fail" (D. Potvin et al., 2008)

Complete thread:

Initial sample size guess for the Potvin methods ElMaestro 2017-08-19 15:04
- Initial sample size guess for the Potvin methods Helmut 2017-08-19 16:06
  - Initial sample size guess for the Potvin methodsElMaestro 2017-08-19 16:14
    - Initial sample size guess for the Potvin methods Helmut 2017-08-19 17:12
      - Initial sample size guess for the Potvin methods ElMaestro 2017-08-19 17:17
        
        Confuse-a-Cat Helmut 2017-08-19 17:33
        
        Confuse-a-Cat ElMaestro 2017-08-19 17:56
    - loop ↔ vectorized ↔ direct Helmut 2017-08-20 14:40
      - loop ↔ vectorized ↔ direct ElMaestro 2017-08-20 15:22
        
        loop ↔ vectorized ↔ direct Helmut 2017-08-20 16:23
        
        loop ↔ vectorized ↔ direct ElMaestro 2017-08-20 17:22
- The n ext crackpot iteration ElMaestro 2017-08-19 20:04
  - The n ext crackpot iteration Helmut 2017-08-20 02:20
- The ultimate crackpot iteration! ElMaestro 2017-08-20 14:35
  - The ultimate crackpot iteration! Helmut 2017-08-20 15:11
    - The ultimate crackpot iteration! ElMaestro 2017-08-20 15:28
      - The ultimate crackpot iteration! Helmut 2017-08-20 16:06
        
        The ultimate crackpot iteration! ElMaestro 2017-08-20 16:15
        
        The ultimate crackpot iteration! Helmut 2017-08-20 18:58
        
        The ultimate crackpot iteration! ElMaestro 2017-08-20 19:32
        
        Suggested code ElMaestro 2017-08-21 18:13
        
        Nitpicker! Helmut 2017-08-22 13:33
        
        Nitpicker! ElMaestro 2017-08-22 17:27
        
        Nitpicker! Helmut 2017-08-22 17:49
        
        Nitpicker! ElMaestro 2017-08-22 17:59
        
        Nitpicker! Helmut 2017-08-22 19:15
        
        Benchmark code ElMaestro 2017-08-22 22:29
        
        Benchmark code Helmut 2017-08-23 01:48