Re: st: detectable alternative/effect size;

[Steven Samuels <sjhsamuels@earthlink.net>]

-

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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