[R] Sample size calculation for differences between two very small proportions (Fisher's exact test or others)?

[Mitchell Maltenfort]

Not with R, but look for G*Power3, a free tool for power calc,
includes FIsher's test.

http://www.psycho.uni-duesseldorf.de/abteilungen/aap/gpower3

On Mon, Nov 8, 2010 at 10:52 AM, Giulio Di Giovanni
<perimessaggini at hotmail.com> wrote:
>
>
> Hi,
> I'm try to compute the minimum sample size needed to have at least an 80% of power, with alpha=0.05. The problem is that empirical proportions are really small: 0.00154 in one case and 0.00234. These are the estimated failure proportion of two medical treatments.
> Thomas and Conlon (1992) suggested Fisher's exact test and proposed a computational method, which according to their table gives a sample size of roughly 20000. Unfortunately I cannot find any software applying their method.
> -Does anyone know how to estimate sample size on Fisher's exact test by using R?
> -Even better, does anybody know other, maybe optimal, methods for such a situation (small p1 and p2) and the corresponding R software?
>
> Thanks in advance,
> Giulio
>
>
>
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