[R] fisher exact for > 2x2 table

viostorm rob.schutt at gmail.com
Fri Apr 29 17:43:53 CEST 2011


After I shared comments form the forum yesterday with the biostatistician he
indicated this:

"Fisher's exact test is the non-parametric analog for the Chi-square 
test for 2x2 comparisons. A version (or extension) of the Fisher's Exact 
test, known as the Freeman-Halton test applies to comparisons for tables 
greater than 2x2. SAS can calculate both statistics using the following 
instructions.

  proc freq; tables a * b / fisher;"

Do people here still stand by position fisher exact test can be used for RxC
contingency tables ?  Sorry to both you all so much it is just important for
a paper I am writing and planning to submit soon. ( I have a 4x2 table but
does not meet expected frequencies requirements for chi-squared.)

I guess people here have suggested R implements, the following, which
unfortunately are unavailable at least easily at my library but  at least by
the titles indicates it is extending it to RxC 

Mehta CR, Patel NR. A network algorithm for performing Fisher's exact test
in r c contingency tables. Journal of the American Statistical Association
1983;78:427-34.
 
Mehta CR, Patel NR. Algorithm 643: FEXACT: A FORTRAN subroutine for Fisher's
exact test on unordered r x c contingency tables. ACM Transactions on
Mathematical Software 1986;12:154-61.

The only reason I ask again is he is exceptionally clear on this point.

Thanks again, 

-Rob



viostorm wrote:
> 
> Thank you all very kindly for your help.
> 
> -Rob
> 
> --------------------------------
> Robert Schutt III, MD, MCS 
> Resident - Department of Internal Medicine
> University of Virginia, Charlottesville, Virginia
> 

viostorm wrote:
> 
> Thank you all very kindly for your help.
> 
> -Rob
> 
> --------------------------------
> Robert Schutt III, MD, MCS 
> Resident - Department of Internal Medicine
> University of Virginia, Charlottesville, Virginia
> 


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