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Re: st: detectable alternative/effect size;


From   Steven Samuels <sjhsamuels@earthlink.net>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: detectable alternative/effect size;
Date   Tue, 16 Sep 2008 16:34:02 -0400

-

Elliot, Power depends on the values of the two probabilities being compared. You will need to specify at least one of the them (most conveniently the smaller- use the RR to compute the second one). The following gives sample sizes for pairs of probabilities, all with RR = 2.00

sampsi .1 .2, pow(.9)
sampsi .3 .6, pow(.9)
sampsi .01 .02, pow(.9)

-Steve

On Sep 16, 2008, at 4:18 PM, Elliott Dasenbrook wrote:


Hi,

I am trying to calculate the detectable alternative for a dichotomous outcome expressed as a relative risk given my sample size and a power of 0.90;
Is there a command/package in STATA that does this? [i saw that this can be calculated for Cox proportions]
The sampsi command only allows calculation of power or sample size as far as I can tell;

Thank you,

Elliott
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