merciless tester! [🇷 for BE/BA]

posted by Helmut Homepage – Vienna, Austria, 2016-03-07 19:56 (3258 d 13:44 ago) – Posting: # 16071
Views: 10,874

Hi Shuanghe,

❝ I noticed that at certain combinations PowerTOST would produce errors. e.g., with the following values

❝ sampleN.scABEL(alpha = 0.05, targetpower = 0.8, theta0 = 0.91,

❝                     CV = 0.1, design = "2x2x4", regulator = "EMA")

❝ would produce error

Error in if (pwr <= targetpower) cat(n, " ", formatC(pwr, digits = pd,  :

❝   missing value where TRUE/FALSE needed

Confirmed.

❝ These error only appear when CV is extremely low so in practice it doesn't matter since no one will use 2x2x4 replicate study for product with ISCV of 10%.


Right. :-D

❝ […] can anyone tell me what's going on here? Maybe it's apparent for R gurus but as R novice I have no idea what the message says.


At such a low CV you could use sampleN.TOST() to get a first idea:
library(PowerTOST)
x <- sampleN.TOST(targetpower = 0.8, theta0 = 0.91,
                  CV = 0.1, design = "2x2x4",
                  details = FALSE, print = FALSE)
cat(paste0("n = ", x[["Sample size"]], ", power = ",
           signif(x[["Achieved power"]], 6), "\n"))
n = 6, power = 0.913161


Looking at the source (type sampleN.scABEL in the console) we find
nmin <- 6
down <- FALSE

so I guess it could be possible. Needs some additional error-trapping. Detlew?

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