Message-ID: <loom.20090322T033723-111@post.gmane.org>
Date: 2009-03-22T03:42:08Z
From: Ben Bolker
Subject: Fisher test problem
<markleeds <at> verizon.net> writes:
>
> by definition, the one tailed p-value has to be <= 0.5 so there is
> still something wrong with your OpenEpi calc. Most likely it's
> calculating the
> 2 tailed p-value and then mistakenly multiplying by 2. For example:
For what it's worth, Fisher's exact test with alternative="greater"
(true odds ratio is > 1) does give 0.6273 in R. (Why does a one-tailed
test have to have p<=0.5? The probability that a test statistic
is greater than some null-hypothesis value can be anywhere
between 0 and 1 ...) It is a 1-tailed test,
but (as has been pointed out) multiplying it by 2 without
truncating at 1 is wrong.
Ben Bolker