Re: [R] Fisher test problem

From: <markleeds_at_verizon.net>
Date: Sat, 21 Mar 2009 22:51:18 -0500 (CDT)


  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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https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. Received on Sun 22 Mar 2009 - 02:55:58 GMT

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