Fisher'S Exact Test And Odds Ratio

Question

[Diana]

Hello everyone,

Im trying to perform Fisher's exact test in R. Im calculating odds ratio like this

(no.of successes in my set) X (no. of failures in background set) / (no.of successes in background set X no. of failures in my set)

In the denominator i get 0 for some cases because failures in my set are 0 for some cases.

Can anyone tell me how to calculate p-values from odds ratio? Also what does it mean if we say odds ratio should be greater or less than 1?if I want to test over-representation in my set against the background set what should be the odds ratio and how can I calculate that?

Many thanks.

[Michael Kuhn]

you are more likely to find an expert on the Statistics StackExchange: http://stats.stackexchange.com/

Answer 1

[Neilfws]

Too many questions in one :)

The short answer: this issue has been discussed at Stats StackExchange; they recommend studying this PDF and using the associated R package, aylmer.

[brentp]

thanks, that PDF is very informative.

[Dataman]

The PDF is not available via the provided link possibly due to removal of the aylmer package from cran. This link may point to the PDF in question. brentp, could you please confirm that this link points to the PDF in question? Thank you! :)