TSD statistical model - with multiple sites [Two-Stage / GS Designs]

posted by Helmut Homepage – Vienna, Austria, 2021-10-12 13:27 (785 d 19:26 ago) – Posting: # 22625
Views: 1,225

Hi d_stat,

❝ ❝ […] Originally we wanted to go with a variant of ‘Method C’ cause it’s slightly more powerful (esp. when you expect to stop in the IA with BE) and it is preferred by the FDA.

❝ Thus, we are sticking to Potvin.

I wouldn’t. It might be that the site-model mentioned above is not stable. When I tried to add ‘sites’ to Potvin’s ‘Example 2’ (subjects 1–4: 1, 5–8: 2, 9–12: 3), Phoenix/WinNonlin showed me the finger.

❝ In order to do the validations for multiple-site nature of the study we are thinking of amending the code in the Power2Stage, since it's not part of package yet. Am I wrong to assume the amendment will be connected to decreasing of df for the error term with the number planned sites, …

That’s correct.

❝ … or is there any other part that I am missing?

You would also have to modify the degrees of freedom in the function to re-estimate the sample size (sampsiz2.R).

❝ Of course, the alternative is always to encourage (pray to) the holy trinity to update the package ;-)

Sorry. I'm afraid your prayers will not be answered.

Maurer’s method as implemented in Power2Stage allows already to provide the degrees of freedom and the standard error of the means of a more complex model than the conventional 2×2×2 crossover.Hence, why the efforts?

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