[R] Fisher test accuracy in doubt
hadley wickham
h.wickham at gmail.com
Sun Mar 22 01:05:15 CET 2009
On Sat, Mar 21, 2009 at 2:03 PM, joker77 <vijumoses at gmail.com> wrote:
>
> Hi, I noted a discrepancy between R and openepi when I ran a fisher test with
> the same matrix. In R:
>
>> a=matrix(c(1,2,6,17), nrow=2)
>> a
> [,1] [,2]
> [1,] 1 6
> [2,] 2 17
>> fisher.test(a, conf.int=T)
>
> Fisher's Exact Test for Count Data
>
> data: a
> p-value = 1
> alternative hypothesis: true odds ratio is not equal to 1
> 95 percent confidence interval:
> 0.02061498 31.73691924
> sample estimates:
> odds ratio
> 1.396646
>
> But in openepi the P value is 1.25. (In another instance too for other sets
> of data, I had got a p value of 1 in 3 instances for a prop.test when I got
> 3 other answers on a friend's stata software with the same data. )
Given that a p-value is between 0 and 1, I would rather think that
openEpi's accuracy is in doubt.
Hadley
--
http://had.co.nz/
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