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Science Forum Index » Statistics - Math Forum » Sample size calculation with non-inferiority log-rank...
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| juanvte202 at (no spam) googlemail.com... |
 Posted: Wed May 07, 2008 11:23 pm |
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Guest
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Some days ago I ask for a suggestions about how to calculate the
necessary sample size to proof non-inferiority with censored data. I
found out a paper and an equation to do these calculations but now,
after further study, I am very surprised with the implications of this
equation.
The formula is:
m = 4(Z(1-alfa)+Z(1-beta))^2 / ln(delta)^2
Z(x) is the inverse normal standard distribution and delta is the non-
inferiority range.
This equation is telling us that the sample size for a non-inferiority
test with survival data depends only of the non-inferiority range.
Therefore, the sample size is independent to the observed Hazard Rate
or possible deviations, parameters which are very important in other
non-inferiority tests as for example non-inferiority for two means. No
matter if my experimental drug is usually superior to the active
control, the only parameter that affects the selection of the sample
size is the non-inferiority range!!
Does somebody know if these interpretations are correct? I think that
it is a hard affirmation and I would to be confident before do it.
Thanks in advance.
Sincerely,
Juan Vicente Torres. |
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