Regulatory acceptance of PowerTOST [Software]
» In Russia we have two options to prove sample size: either demonstrate calculations with formulas …
See this presentation (slide 8). The procedure is always iterative (since the t-value in the formula to calculate power depends on the degrees of freedom and hence, the sample size itself). The approximation1 by the shifted central t-distribution can be done with a pocket calculator (alternatively: paper-pencil-brain) and a t-table. The better approximation (noncentral t) already needs software, since no tables exist for a range of the noncentrality parameter. The exact method needs numeric integration of two integrals → software.
» … or provide literature reference.
What do you mean by that?
» The 1st option is not for me because I don't have relevant background so I'd prefer the 2nd way.
» So, if somebody could share any literature reference in a journal (preferrable) which mentions PowerTOST I'd really appreciate it
Jones & Kenward2
The power and sample size for a bioequivalence trial can conveniently be calculated using the R package PowerTOST (Labes (2013)).a
The power is calculated using the R package PowerTOST (Labes (2013)) with the “exact” option.b
Using the PowerTOST (Labes (2013)) R library function, the power, for a true ratio of 1, for this estimated CV and a total sample size of 20 is just over 0.04.c
PowerTOST is mentioned in Nadarajah et al.3
In the folder
\library\PowerTOST\testsyou find R-scripts to validate the various sample size functions against published data. See the man-pages of
ctSJ.VIII.20for the references.
- Hauschke, D, Steinijans, VW, Diletti E, Burke M. Sample Size Determination for Bioequivalence Assessment Using a Multiplicative Model.
J Pharmacokin Biopharm 1992;20(5);557–61. doi:10.1007/BF01061471.
- Jones B, Kenward MG. Design and Analysis of Cross-Over Trials.
Boca Raton: CRC Press / Chapman & Hall; 3rd ed. 2015.
Stat Meth. 2015;22:23–46. doi:10.1016/j.stamet.2014.07.002. open source.
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