Sridhar.E
☆

India,
2021-04-27 14:49
(54 d 18:37 ago)

Posting: # 22331
Views: 673

## inter subject CV to intra subject CV [Power / Sample Size]

Hai all,

can any one help how i convert inter subject CV to intra subject CV for sample size estimation.

regards.,

Sridhar

Edit: Category changed; see also this post #1[Helmut]
Helmut
★★★

Vienna, Austria,
2021-04-27 15:14
(54 d 18:12 ago)

@ Sridhar.E
Posting: # 22332
Views: 561

## No relationship between CVinter and CVintra

Hi Sridhar,

» can any one help how i convert inter subject CV to intra subject CV for sample size estimation.

What do you mean by ‘convert’? It’s like saying ‘convert an apple to an orange’. Both are approximately spherical fruits, more or less sweet and of similar weight. However, they are exclusively distinct.

If you have a crossover study, both CVs are accessible. If you have a parallel design, you get only the total (aka pooled) CV (see this article). There is an infinite number of combinations of CVinter and CVintra which will give the same CVtotal.
$$\begin{matrix} s_\textrm{inter}^2=\log_{e}(CV_\textrm{inter}^2+1)\\ s_\textrm{intra}^2=\log_{e}(CV_\textrm{intra}^2+1)\\ CV_\textrm{total}=\sqrt{\exp\left(s_\textrm{inter}^2+s_\textrm{intra}^2-1\right)} \end{matrix}$$

Dif-tor heh smusma 🖖
Helmut Schütz

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