[R] fisher.test - can I use non-integer expected values?

bakerwl bakerwl at uwyo.edu
Wed Dec 11 03:55:09 CET 2013


David,

Thanks for your reply--I appreciate your thoughts. I will look at prop.test.

The reason I chose fisher.test over chisq.test is that fisher.test is more
appropriate when observed counts are not numerous--empty cells and cells
with counts < 5 are less a problem. 

Expected values are needed to test a null hypothesis against observed
counts, but if total observed counts are 20 for 3 categories, then a null
hypothesis of a random effect would use expected values = 6.67 in each of
the 3 categories (20/3). 

Yes, fisher.test is for count data and so is chisq.test, but chisq.test
allows 6.67 to be input as expected values in each of 3 categories, while
fisher.test does not seem to allow this? 

I don't think it is inherent in Fisher's exact test itself that expected
values must be integers, but not sure.





--
View this message in context: http://r.789695.n4.nabble.com/fisher-test-can-I-use-non-integer-expected-values-tp4681976p4681989.html
Sent from the R help mailing list archive at Nabble.com.



More information about the R-help mailing list