Bioequivalence and Bioavailability Forum

Naïve distribution [General Sta­tis­tics]

posted by d_labes  – Berlin, Germany, 2013-05-06 11:02 (4802 d 12:40 ago) – Posting: # 10543
Views: 4,760

Dear Helmut,

❝ P.S.: Any idea why I get unequal variances of T and R in ~28% of studies? I expect only ~5%…

IMHO you are simulating the untransformed metrics (whatever it may be named: Cmax, AUC, ...) if you use rlnorm().
Thus change to:

# log-transformed data are normal distributed
T <- c(T, rnorm(group1, mean=log(GMR), sd=CV2se(CV1))
R <- c(R, rnorm(group2, mean=0, sd=CV2se(CV1))

and all is right with the world :

Expected GMR: 0.95 – total CV 50 %.
Total sample size for = 80 % power: 194
Average study size: 196 ( 195 – 198 )
In 80.4 % of 10000 simulated studies BE was demonstrated.
Note: Unequal variances of T and R (F-test p <0.05) in 5.12 % of studies.

Complete thread:

• Simulating center and group effects Helmut 2013-05-04 21:05 
  • Simulating center and group effects ElMaestro 2013-05-05 00:31
    • Naïve pooling? Helmut 2013-05-05 14:34
      • Naïve pooling? ElMaestro 2013-05-05 18:20
      • Naïve distributiond_labes 2013-05-06 09:02
        • Naïve distribution Helmut 2013-05-06 10:56