Bioequivalence and Bioavailability Forum • sample size in bioequivalence studies

sample size in bioequivalence studies [Power / Sample Size]

posted by daryazyatina – Ukraine, 2017-08-03 12:58 (2784 d 12:37 ago) – Posting: # 17650
Views: 20,040

Hi ElMaestro,

❝ Good choice :-D

Thank you

❝ Can you tell what your design is and which values you want to plug in for the calculation? If the difference is 2 or 4 subjects, then so be it, subtle differences in approximation may account for that. If the difference is 46 or something then I'd wonder, too. I am sure there is an explanation and that your confidence in the powerTOST package can easily be restored.

For comparison, I use all the standard properties. Design 2x2, confidence intervals 0.8 - 1.25, power 0.8, alpha 0.05.
The only thing about what I'm not sure is CV. Because in formula that I used this is intra-subject variability, but in PowerTOST() this is coefficient of variation as ratio. In calculations in both cases I used СV - 0.3.

And this is results from sampleN.TOST()
sampleN.TOST(logscale = TRUE, CV = 0.3, details = TRUE)

+++++++++++ Equivalence test - TOST +++++++++++

            Sample size estimation

-----------------------------------------------

Study design:  2x2 crossover 

log-transformed data (multiplicative model)



alpha = 0.05, target power = 0.8

BE margins = 0.8 ... 1.25 

True ratio = 0.95,  CV = 0.3



Sample size (total)

 n     power

40   0.815845

The sample size by the formula I used:

n=28

❝ Apart from that you are of course right if you intended to hint that the author of the power.TOST family of R functions is a dubious character.

Complete thread:

sample size in bioequivalence studies daryazyatina 2017-08-03 09:34 [Power / Sample Size]
- sample size in bioequivalence studies BE-proff 2017-08-03 09:55
  - sample size in bioequivalence studies daryazyatina 2017-08-03 10:08
- sample size in bioequivalence studies ElMaestro 2017-08-03 10:17
  - sample size in bioequivalence studiesdaryazyatina 2017-08-03 10:58
    - sample size in bioequivalence studies DavidManteigas 2017-08-03 12:40
      - sample size in bioequivalence studies daryazyatina 2017-08-03 13:46
      - Don’t use the formula by Chow, Shao, Wang! Helmut 2017-08-03 15:37
        
        Don’t use the formula by Chow, Shao, Wang! daryazyatina 2017-08-03 15:52
        Don’t use the formula by Chow, Shao, Wang! DavidManteigas 2017-08-03 16:12
        
        Don’t use the formula by Chow, Shao, Wang! Helmut 2017-08-03 16:33
        
        Don’t use the Book by Chow, Shao, Wang! d_labes 2017-08-16 16:01
    - compromised power Helmut 2017-08-03 16:04
      - compromised power daryazyatina 2017-08-04 08:15
        
        terminology Helmut 2017-08-04 12:41
        
        terminology daryazyatina 2017-08-16 10:12
        
        terminology Helmut 2017-08-16 18:54
- sample size in bioequivalence studies balinskyi 2018-06-03 12:58