Exact (Owen’s Q) [Power / Sample Size]
❝ […] 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 -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!
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- Choosing formula for sample size Imph 2021-10-20 11:03 [Power / Sample Size]
- Exact (Owen’s Q)Helmut 2021-10-20 11:36