On Tue, 31 Aug 2004, Caimiao Wei wrote:
> Dear all,
>
> Could any one please tell me the exact formula R uses to calculate the
> sample size for one-sample and two-sample t-tests? Thanks,
There isn't a formula in closed form. The exact procedure is in the code.
In words: the critical value for the t-test comes from a t-distribution.
The distribution of the t-statistic under the alternative is a non-central
t-distribution, and the sample size is adjusted to get the requested
power.
-thomas
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