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Re: st: Sample size for non inferiority trial


From   "Joseph Coveney" <jcoveney@bigplanet.com>
To   "Statalist" <statalist@hsphsun2.harvard.edu>
Subject   Re: st: Sample size for non inferiority trial
Date   Tue, 13 Nov 2007 00:18:15 +0900

Alvine Bissery wrote:

I'd like to estimate the sample size for a non inferiority clinical trial.
We have 2 surgery techniques, A and B, and we compare quality of life score
after surgery.
For surgery A, the score is 180 (the max for this score level is 200)
We would like that the score with surgery B be not inferior to 165

Standard deviation is ~20

Is there a way to estimate sample size for non inferiority trial with Stata?

--------------------------------------------------------------------------------

The simplest way is to use -sampsi , onesided-, flipping alpha and beta (1 -
power).  But that might not work well, because you have an expected quality
of life score that's a standard deviation away from the ceiling.  For that
reason, you might want to consider simulation as an alternative.  There is
an FAQ at http://www.stata.com/support/faqs/stat/power.html .  The author of
that FAQ also wrote a detailed article:  A. H. Feiveson (2002) Power by
simulation. _The Stata Journal_ 2(2):107--24.

You'll need to assure a plausible distribution when generating the data.

Joseph Coveney

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