# [R] Fisher test problem

C.H. chainsawtiney at gmail.com
Sun Mar 22 03:07:29 CET 2009

```I tried the OpenEpi, the p-value of 1.25 is due to the fact that the
one tailed p-value is 0.62. The two tailed p-value then is 0.62 * 2 =
1.25. OpenEpi is not clever enough to ceiling the p-value to 1.

CH

On Sun, Mar 22, 2009 at 3:43 AM, David Winsemius <dwinsemius at comcast.net> wrote:
> 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?
>>
>>
>> Viju Moses
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>
> David Winsemius, MD
> Heritage Laboratories
> West Hartford, CT
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> and provide commented, minimal, self-contained, reproducible code.
>

--
CH Chan
Research Assistant - KWH
http://www.macgrass.com

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