thanks ben: i think my example makes sense but my terminology of one tailed two tailed was wrong or flipped or whatever. in fact, that's why i gave the example. i wasn't remembering the terminology because it's been too long since i stepped in a classroom ( 8 years ).
On Sat, Mar 21, 2009 at 10:42 PM, Ben Bolker wrote:
<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
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