Rules of Thumb (PASS) [Power / Sample Size]

posted by Helmut Homepage – Vienna, Austria, 2022-07-24 16:55 (132 d 21:43 ago) – Posting: # 23162
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Hi Dennis,

❝ Thank you very much for your suggestions.


Welcome.

❝ Your paper is very interesting and so professional.


Just a collection of desultory thoughts – not a peer-reviewed paper. Maybe it’s all crap. :-D

❝ And we will try to calculate the sample size with all pairwise treatment comparisons.


OK. Still: Are you targeting superiority or equivalence? Yin and Yang.

❝ Notablly, you said that all versions of PASS require the standard deviation of the treatment difference as input.


That was my experience before I deleted it from my machine two years ago.

❝ However, the paper of the Pilot Study Sample Size Rules of Thumb in PASS Sample Size Software Documentation did not present the standard deviation or any other parameter (see figure2 and figure3)


That’s not a paper but part of the manual, which is available online. In the future please don’t post screenshots in JPG-format, use PNG instead. JPEGs are blurred and full of compression artefacts making them difficult to read.

❝ Did we ignore any important information?


No idea. I don’t own the book of Machin et al. and hence, can’t tell. Will check Whitehead et al.,1 time allowing.
That’s the problem with software (not limited to commercial ones). If the documentation is not exhaustive, you never know what’s going on under the hood2 when you click the button.


  1. Whitehead AL, Julious SA, Cooper CL, Campell MJ. Estimating the sample size for a pilot randomised trial to minimise the overall trial sample size for the external pilot and main trial for a continuous outcome variable. Stat Meth Med Res. 2016; 25(3): 1057–73. doi:10.1177/0962280215588241 [image] Free Full text.
  2. For some observations see this thread. :thumb down:

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