# st: R: Sample size for non inferiority trial

 From "Carlo Lazzaro" To Subject st: R: Sample size for non inferiority trial Date Mon, 12 Nov 2007 17:53:04 +0100

```Alvine wrote:

Dear all,

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
?

Thank you

Alvine Bissery

*****************************************************
Alvine BISSERY
Ingénieur statisticien
Service de Biostatistique des Hospices Civils de Lyon
162 Avenue Lacassagne
69424 Lyon Cedex 03 - France
tél: +33 4 72 11 57 55
fax: +33 4 72 11 51 41

Dear Alvin,

that the answer might sound like the following example:
----------------------begin example-----------------------
sampsi 180 165, p(.90) sd(20)

Estimated sample size for two-sample comparison of means

Test Ho: m1 = m2, where m1 is the mean in population 1
and m2 is the mean in population 2
Assumptions:

alpha =   0.0500  (two-sided)
power =   0.9000
m1 =      180
m2 =      165
sd1 =       20
sd2 =       20
n2/n1 =     1.00

Estimated required sample sizes:

n1 =       38
n2 =       38

----------------------end example-----------------------
Fore more on this topic, I would take the liberty to refer you to the
following textbooks:

Juul S: An Introduction to Stata for Health Researchers. Stata Press, 2006

Peacock J, Kerry S. presenting medical statistics from proposal to
publications. Oxford University Press, 2007
HTH and Kind Regards,

Carlo

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```