[R] Fisher test problem

[David Winsemius]

Let me ask you: What degree of credibility should be accorded a WWW  
application that delivers a p-value of 1.25?

If the answer is not immediately and glaringly obvious, then tell us,  
what sort of axioms of probability are you working with?

-- 
David Winsemius
On Mar 21, 2009, at 3:17 PM, Viju Moses 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. )
>
> I'm using R on Ubuntu Intrepid. Is there anything I'm doing wrong?  
> Any other packages I have to install?
>
> Thanks in advance
>
> Viju Moses
>
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David Winsemius, MD
Heritage Laboratories
West Hartford, CT