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Re: st: RE: RE: sampsize formula


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: RE: sampsize formula
Date   Thu, 3 Nov 2011 19:50:48 +0000

This is part of the .pdf documentation in Stata 11 and 12.

Nick

On Thu, Nov 3, 2011 at 7:40 PM, Sara Borelli <sborelli@impaqint.com> wrote:

> Thank you Sarah
> The problem is that we do not have access to the manuals right now, but the reference helps a lot
Sarah Edgington

> Do you have access to the Stata base reference manuals?
> Typically the manuals contain detailed information on the formulas used to
> implement a command.  The manual entry for -sampsi- is no exception. It's in
> the section titled "Methods and formulas" near the end of the entry.

Sara Borelli

> I would like to know the exact formula beyond the sampsi command to
> calculate the sample size of two groups using comparison of means :
>
> sampsi     m1  m2,  sd1()  sd2()  power ()  alpha()
>
> the output gives me the sample size of the two groups, n1 and n2, but I
> would need the exact mathematical formula

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