[R] exact conditional mantelhaen.test estimate is 0 ?!
Thomas Lumley
tlumley at u.washington.edu
Fri Jul 8 19:34:19 CEST 2005
On Fri, 8 Jul 2005, Florian Hahne wrote:
> Dear listers,
>
> I am trying to compute the exact conditional test given strata margins
> of a 2 by 2 by K array using the mantelhaen.test function to get a
> common odds ratio estimate.
> The estimate for the test on the following data is 0, which in my
> opinion dosen't make any sense.
>
Indeed it doesn't. Some probabilities are underflowing to zero. It is
informative to look at the estimates from
mantelhaen.test(round(x/s), exact=TRUE)
for various values of s. The estimate is stable at about 0.04 for
large s until s gets to just above 1.8, then quickly decreases to zero.
I think you need exact=FALSE for data sets this large.
-thomas
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