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# Re: st: re: non-inferiority trials

 From "Niemierko, Andrzej" To "statalist@hsphsun2.harvard.edu" Subject Re: st: re: non-inferiority trials Date Fri, 5 Oct 2012 17:25:49 +0000

```Thanks, Phil, for the CONSORT link. It's most useful.
Yes, I'm aware that the p value depends on an apriori chosen "delta" (or
margin) and it's a one-sided test. I was just wondering if there exist a
Stata ado program that can handle this.
Andrzej

On 10/5/12 12:37 PM, "Philip Jones" <pjones.statalist@gmail.com> wrote:

>
>On Thursday, October 4, 2012, Niemierko, Andrzej wrote:
>
>> Are there any user-written Stata programs to calculate:
>> 1. the confidence interval for the difference of median survival times,
>>and
>> 2. p values in non-inferiority trials?
>>
>> Thanks,
>> Andrzej
>
>
>Regarding #2, how can one calculate a P value for a non-inferiority trial?
>I believe there is a logical error when discussing this, as explained
>below.
>
>Null hypothesis in a non-inferiority trial: there is a difference between
>groups.
>
>Alternate hypothesis: there is no difference between groups, up to a
>certain acceptable difference (the "delta"). Note this is a one-sided
>check, as opposed to an equivalence trial.
>
>Therefore, the P value will be dependent on your delta. If you choose a
>ridiculously high, implausible delta, you may have a significant P value
>but clear evidence of a difference between groups. Better to use a
>one-sided confidence interval approach as recommended in the CONSORT
>guidelines at
>http://www.consort-statement.org/extensions/designs/non-inferiority-and-eq
>uivalence-trials/
>
>Phil
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