Bioequivalence and Bioavailability Forum • compromised power

compromised power [Power / Sample Size]

posted by Helmut – Vienna, Austria, 2017-08-03 18:04 (3239 d 11:47 ago) – Posting: # 17655
Views: 22,657

Hi Darya,

❝ The sample size by the formula I used:

❝ n=28

To keep everything equal you should convert the standard deviation to the CV. Hence,

library(PowerTOST) sampleN.TOST(CV=se2CV(0.3)) +++++++++++ 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 = 0.3068783 Sample size (total) n power 42 0.818541

Of course higher than the 28 by the dubious formula. As David mentioned above (quoting Zhang’s paper) power is compromised. Let’s check how much:

power.TOST(CV=se2CV(0.3), n=28) [1] 0.6250166

Oops!

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Complete thread:

sample size in bioequivalence studies daryazyatina 2017-08-03 09:34
- 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 studies daryazyatina 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 powerHelmut 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