Bioequivalence and Bioavailability Forum

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

posted by Helmut  – Vienna, Austria, 2021-10-20 13:36 (1084 d 19:06 ago) – Posting: # 22644
Views: 4,151

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 -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! 
Helmut Schütz


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Complete thread:

• Choosing formula for sample size Imph 2021-10-20 11:03 [Power / Sample Size] 
  • Exact (Owen’s Q)Helmut 2021-10-20 11:36
    • Exact (Owen’s Q) Imph 2021-10-20 12:53
      • Exact (Owen’s Q) Helmut 2021-10-20 13:26
        • Exact (Owen’s Q) Imph 2021-10-24 10:41
          • n iteratively from power Helmut 2021-10-24 10:54
          • aproximate n d_labes 2021-10-24 19:26
        • Exact (Owen’s Q) Willem Talloen 2022-09-01 15:48
          • PowerTOST & FDA Helmut 2022-09-01 16:31