st: Fisher's exact P and -csi-

[Garry Anderson <g.anderson@unimelb.edu.au>]

Hi,

I am enquiring why the value of Fisher's exact P for a 2 x 2 table should 
decrease when there is a smaller sample size for each of the two samples 
and the two proportions remain at 100% and 0%?

For example
-csi 6 0 0 6,e-
                               1-sided Fisher's exact P = 0.0011
                               2-sided Fisher's exact P = 0.0022

-csi 5 0 0 5,e-
                                1-sided Fisher's exact P = 0.0000
                                2-sided Fisher's exact P = 0.0000

-csi 4 0 0 4,e-
                                1-sided Fisher's exact P = 0.0143
                                2-sided Fisher's exact P = 0.0286

-csi 3 0 0 3,e-
                                1-sided Fisher's exact P = 0.0000
                                2-sided Fisher's exact P = 0.0000

-csi 2 0 0 2,e-
                                1-sided Fisher's exact P = 0.0000
                                2-sided Fisher's exact P = 0.0000

-csi 1 0 0 1,e-
                                1-sided Fisher's exact P = 0.5000
                                2-sided Fisher's exact P = 1.0000

Any suggestions would be appreciated.

(SPSS gives P=0.1 for the 3 0 0 3 combination)

I am using Stata 8.2, 30 Jan 2004, ado 11 Mar 2004.

Kind regards, Garry

Garry Anderson
School of Veterinary Science
University of Melbourne
250 Princes Highway           Ph  03 9731 2221
WERRIBEE    3030             Fax  03 9731 2388
Email:  g.anderson@unimelb.edu.au 
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