[R] Fisher test accuracy in doubt

joker77 vijumoses at gmail.com
Sat Mar 21 20:03:54 CET 2009

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 

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
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