Bioequivalence and Bioavailability Forum

Hi Mittyri,

Of course, ElMaestro is right.

There Can Be Only One.

❝ do I understand it right that if the study is terminated after 1st stage (due to any reason), we are using the same function with n1 (not fixing n2 to 0)

Not sure what you mean. For any of the simulated studies the decision scheme of the method is followed. The function returns counters for the studies passing in the 1^st stage (pBE_s1) and of the pooled data in the 2^nd stage (pBE). We can extract all numbers:

library(Power2Stage)
# using defaults of method = "B"
tmp <- power.tsd(CV = 0.2, n1 = 12, theta0 = 1.25)
if (tmp$theta0 == tmp$theta1 | tmp$theta0 == tmp$theta2) {
  txt <- "Type I Error"
} else {
  txt <- "Power"
}
cat(formatC(tmp$nsims, digits = 7, big.mark = ","),
    "simulated studies\nFailed in stage 1     :",
    formatC(tmp$nsims - tmp$nsims * tmp$pBE_s1 - tmp$pct_s2 / 100 * tmp$nsims,
            digits = 6, big.mark = ","),
    sprintf("(%7.4f%%)",
            100 * (tmp$nsims - tmp$nsims * tmp$pBE_s1 - tmp$pct_s2 /
            100 * tmp$nsims) / tmp$nsims),
    "\nPassed in stage 1     :",
    formatC(tmp$pBE_s1 * tmp$nsims, digits = 6, big.mark = ","),
    sprintf("(%7.4f%%)", 100 * tmp$pBE_s1),
    "\nProceeded to stage 2  :",
    formatC(tmp$nsims * tmp$pct_s2 / 100, digits = 6, big.mark = ","),
    sprintf("(%7.4f%%)", tmp$pct_s2),
    "\nFailed in stage 2     :",
    formatC(tmp$nsims * tmp$pct_s2 / 100 - (tmp$pBE -tmp$pBE_s1) * tmp$nsims,
            digits = 6, big.mark = ","),
    sprintf("(%7.4f%%)",
    100 * (tmp$nsims * tmp$pct_s2 / 100 - (tmp$pBE -tmp$pBE_s1) * tmp$nsims) / tmp$nsims),
    "\nPassed in stage 2     :",
    formatC((tmp$pBE -tmp$pBE_s1) * tmp$nsims, digits = 6, big.mark = ","),
    sprintf("(%7.4f%%)", 100 * (tmp$pBE -tmp$pBE_s1)),
    "\nFailed in stage 1 or 2:",
    formatC((1 - tmp$pBE) * tmp$nsims, digits = 6, big.mark = ","),
    sprintf("(%7.4f%%)", 100 * (1 - tmp$pBE)),
    "\nPassed in stage 1 or 2:",
    formatC(tmp$pBE * tmp$nsims, digits = 6, big.mark = ","),
    sprintf("(%7.4f%%) = empiric", 100 * tmp$pBE), txt, "\n")


1,000,000 simulated studies
Failed in stage 1     :  92,550 ( 9.2550%)
Passed in stage 1     :  28,849 ( 2.8849%)
Proceeded to stage 2  : 878,601 (87.8601%)
Failed in stage 2     : 861,177 (86.1177%)
Passed in stage 2     :  17,424 ( 1.7424%)
Failed in stage 1 or 2: 953,727 (95.3727%)
Passed in stage 1 or 2:  46,273 ( 4.6273%) = empiric Type I Error

And:

tmp <- power.tsd(CV = 0.2, n1 = 12, theta0 = 0.95)

100,000 simulated studies
Failed in stage 1     :   2,325 ( 2.3250%)
Passed in stage 1     :  41,333 (41.3330%)
Proceeded to stage 2  :  56,342 (56.3420%)
Failed in stage 2     :  13,409 (13.4090%)
Passed in stage 2     :  42,933 (42.9330%)
Failed in stage 1 or 2:  15,734 (15.7340%)
Passed in stage 1 or 2:  84,266 (84.2660%) = empiric Power

❝ ❝

---

PS: I changed the category from Software. Though you asked for the -package Power2Stage, perhaps somebody would have the balls to roll out own code.

❝

❝ I changed the category twice when wrote the post

I see. Feel free to change it to anyone you like.