For the benefit of us uninformed folks, could someone write a short
piece giving equivalent words (operational definitions) for
Non-inferiority
equivalence
two-side hypothesis for alpha test (group A is equal to group B/
Group A is different than Group B)
one-side hypothesis for alpha test (group A is equal or less than
group B/group A is greater than group B)
one-side and/or two-side beta test (power test) for groups A and B
comparisons.
If my suspicions are right, then Ioanna's questions can be re-phrased
into typical/common statistical language, and the issue of alpha
level (0.05 or 0.025) will become 'obvious.'
Besides, I want to know the terms used by medical people. :)
Jay
On Jan 26, 2006, at 9:33 AM, ioanna gioni wrote:
> Dear all,
>
> I need to calculate the sample size for a non-inferiority trial
> (normal data).
> I have an issue with the choice of alpha in the sample size
> calculation formula. I am not sure if I need to set my type error I
> (alpha) at half the conventional type I error used in two-sided
> confidence intervals.
> Unfortunately, I don’t have access to any sample size calculations
> book that deals with non-inferiority/equivalence issues.
> Searching in the Internet I found various examples where some
> calculate the sample size setting alpha to be 0.05 and some setting
> alpha to be 0.025.
> I know that for the analysis I need to either calculate a two-sided
> 95% confidence interval (equal-tailed) and then use the lower bound
> for testing the hypothesis or calculate one-sided intervals with a
> coverage probability of 97.5%. My issue is if in the sample size
> calculation I set alpha as 0.05 or 0.025.
>
> Any help would be appreciated,
>
> Ioanna
>
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Jay Warner
Principal Scientist
Warner Consulting, Inc.
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