Exact (Owen’s Q) [Power / Sample Size]

posted by Helmut Homepage – Vienna, Austria, 2021-10-20 13:36 (999 d 16:31 ago) – Posting: # 22644
Views: 3,661

Hi Imph,

❝ […] which formula to choose to calculate the number of subjects among all the formulas published: Dilleti, Chow, Julious,...

Diletti (1981), which is exact based on Owen’s Q function. Julious is based on an approximation by the noncentral t-distribution and fine as well.

❝ For now I am using chow's formula, I would like to know if there is a plausible reference that supports its use.

Don’t. Chow’s is based on the shifted central t-distribution and the paper contains typos. See also this post.

I suggest to estimate sample sizes with functions of the [image]-package PowerTOST. All three methods are im­ple­ment­ed, where the exact one is the default.
Whilst in many cases sample sizes based on the shifted central t-distribution will be equal to the others, sometimes estimated sample sizes are larger than necessary. The background is shown in an article.

Dif-tor heh smusma 🖖🏼 Довге життя Україна! [image]
Helmut Schütz

The quality of responses received is directly proportional to the quality of the question asked. 🚮
Science Quotes

Complete thread:

UA Flag
 Admin contact
23,101 posts in 4,857 threads, 1,644 registered users;
82 visitors (0 registered, 82 guests [including 8 identified bots]).
Forum time: 06:07 CEST (Europe/Vienna)

One can show the following: given any rule, however “fundamental”
or “necessary” for science, there are always circumstances
when it is advisable not only to ignore the rule,
but to adopt its opposite.    Paul Feyerabend

The Bioequivalence and Bioavailability Forum is hosted by
BEBAC Ing. Helmut Schütz