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# Re: st: power calculation graphs

 From Neil Shephard To statalist@hsphsun2.harvard.edu Subject Re: st: power calculation graphs Date Fri, 20 Aug 2010 10:04:11 +0000

```On Fri, Aug 20, 2010 at 8:54 AM, Nikolaos Pandis <npandis@yahoo.com> wrote:
> Hi to all.
>
> I was wondering if someone would be able to help me draw the following sample calculation graphs with Stata:
>
> 1. Two arm parallel trial, outcome binary.
>
> A power (y-axis) sample size (x-axis) calculation graph for various failure proportions between trial arms. For example, p1=0.80 and p2=0.85, or p1=0.80 p=0.90 or p1=0.80 p=0.95
>
>
> 2. Two arm parallel trial, outcome continuous.
>
> A power (y-axis) sample (x-axis) calculation graph for various failure proportions between trial arms. For example, m1= 100 and m2= 120 with equal sd1=sd2=10. It would be great if I could vary m1, m2, sd (always sd1=sd2)
>

You can do both of these using the -sampsi- command and could have
found this yourself by typing -search sample size- into Stata.

If you want to do the analysis for a range of values then you should
consider putting each call within a series of nested -forval- loops
and write the results to a file using -postfile- which you can then
read into Stata and draw the graphs you want.

I'll leave the actual coding of this as an exercise for you to work on ;-)

Neil

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