Al Gore Rhythms [🇷 for BE/BA]

posted by Helmut Homepage – Vienna, Austria, 2009-09-29 16:52 (5263 d 03:42 ago) – Posting: # 4269
Views: 38,770

Dear D Labes!

❝ Hope you have already waited for me.


Yesss!

❝ Here are the results of the SAS Proc Power.

❝ Seems the power is calculated in this case totally wrong!


Fascinating.

❝ My own rolled code (relying on Owens Q-functions, undocumented but available in SAS) gives:


That’s the more interesting part (homebrew)!

                        n  % power    n  % power
------------------------------------------------
#1 Diletti et al.       4 >70         6 >90
#2 PASS                 4  72.90
#3 D Labes' SAS code    4  72.9014    6  98.6992
#4 nQuery Advisor 7     4  71.559     6  97.943
#5 R-code               4  66.674     6  98.697
#6 FARTSSIE 1.6         4  66.674     6  98.697
#7 StudySize 2.0.1      4  15.9 (!)   6  93.201


n=4 takes the lead by 4:3! Observations:
#5 (based on Algorithm AS 243) and #6 give identical results. This is not surprising, because the VBA-routine within FARTSSIE was written by Russell V. Lenth, the author of AS 243. #2/3 agree; for n=6 power is comparable with #5/6. #4 calculates lower power than #1-3, but still would suggest n=4. The difference between #1-3 and #5/6 might be due to different algorithms for estimating the noncentral t-distribution (#1/3: ?, #2: AS 243?, #4: AS 184, #5/6: AS 243). #7 uses approximations (Ref. 2 in this post); however, yields conservative results.

Maybe I should contact Dieter Hauschke to join the party…


Edit: Many, many years later.

library(PowerTOST)
res <- data.frame(method = c("exact", "mvt", "nct", "central"),
                  n = NA_integer_, power = NA_real_)
for (j in 1:nrow(res)) {
  res[j, 2:3] <- sampleN.TOST(CV = 0.075, theta0 = 1,
                              targetpower = 0.7,
                              method = res$method[j],
                              print = FALSE)[7:8] }
print(res, row.names = FALSE)

  method n     power
   exact 4 0.7290143
     mvt 4 0.7290142
     nct 6 0.9869738
 central 6 0.9611687


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