Rob--
Your biostatistician has not disagreed with the rest of us about anything
except for his preferred name for the test. He wants to call it the
Freeman-Halton test, some people call it the Fisher-Freeman-Halton test,
but most people call it the Fisher Exact test -- all are the same test.
When he was "adamant you could not do > 2x2", what he was being adamant
about was the name you should use when referring to the test for tables
larger than 2x2. Why he was doing that, I don't know, but I think it is
silly -- he confused you and the rest of us.
He goes on to tell you that to get the Freeman-Halton test in SAS, you use
"tables a * b / fisher". In other words, SAS calls the test "Fisher"
instead of calling it Freeman-Halton. R also calls it "Fisher" and not
Freeman-Halton. I'm like R and SAS and unlike your biostatistician, but
to each his own.
You say that he is "exceptionally clear on this point," which may be true,
but what is the point? The point is that he prefers a different *name*
for the test than the rest of us. Everyone agrees on the math/stat.
Mike
--
Michael B. Miller, Ph.D.
Minnesota Center for Twin and Family Research
Department of Psychology
University of Minnesota
On Fri, 29 Apr 2011, viostorm wrote:
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
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