Achievwin ★ US, 20240220 20:49 (51 d 19:17 ago) Posting: # 23869 Views: 801 

Naïve question: When we use pa.ABE for parallel study N determination output gives N for certain power (e.g. if N=424 for 85% power) is this N is for total (N=424) or per arm (212+212)? Kindly explain. 
d_labes ★★★ Berlin, Germany, 20240222 10:54 (50 d 05:11 ago) @ Achievwin Posting: # 23871 Views: 627 

Dear Achievwin, ❝ When we use pa.ABE for parallel study N determination output gives N for certain power (e.g. if N=424 for 85% power) is this N is for total (N=424) or per arm (212+212)? Call the man page of the function sampleN.TOST() and read under DetailsThe estimated sample size gives always the total number of subjects (not subject/sequence in crossovers or subjects/group in parallel designs – like in some other software packages)." That is valid for all the other sample size estimating functions. The power calculating functions accept a single number as sample size, here also the total. Also accepted a vector of sample sizes, here meaning the sample sizes of groups. — Regards, Detlew 
Achievwin ★ US, 20240222 19:34 (49 d 20:32 ago) @ d_labes Posting: # 23872 Views: 615 

Thank you 
Helmut ★★★ Vienna, Austria, 20240223 11:06 (49 d 04:59 ago) @ Achievwin Posting: # 23877 Views: 576 

Hi Achievwin, diving deeper into the matter. I was guessing your example and show the syntax Detlew mentioned above:
If you are interested in post hoc power (I hope your aren’t…), always give the vector of group sizes. If you give the total sample size, the functions of PowerTOST try to keep groups (or sequences in crossovers) as balanced as possible. If your study was more unbalanced, it will calculate a power which is slightly higher than the true one.
The functions of PowerTOST cannot ‘know’ whether a study was unbalanced. It guesses that only if the total sample size is odd (parallel design) or not a multiple of the number of sequences (crossovers). Otherwise, you don’t get a message like above (because in a parallel design it assumes that n_{1} = n_{2} = n/2). Try this one:
— Diftor heh smusma 🖖🏼 Довге життя Україна! _{} Helmut Schütz The quality of responses received is directly proportional to the quality of the question asked. 🚮 Science Quotes 