Fisher Exact Test?

Question

Currently, I'm doing an analysis using Chi-Square test. I realise that the expected frequency is less than 5.

So, I decided to use Fisher exact test.

I'm currently doing a statistic test to see whether the involved variables are statistically significant.

1. Is the Fisher exact test is only used for 2X2 table only. Can I also used for other tables matrices like 3X2, 4X2.
2. How do i perform this test?

Answer 1

When I took a biostatistics course, I only remember the Fisher Exact Test to be for 2X2 only. Here is a website that I used when I was in the course with an applet to calculate it for you; it's very long and tedious by hand.

http://www.psych.ku.edu/preacher/fisher/fisher.htm

It describes rather well how to perform the test.

Hope this helps!

Answer 2

Copied from Statistica 7.0:
"For small n, this probability can be computed exactly by counting all possible tables that can be constructed based on the marginal frequencies" (Statistics in Crosstabulations - Fisher Exact Test)

This software only does it for 2x2, but the real problem is the size of n since "counting all possible tables" grows more than exponentially. (n is the sum of all cells) Note that you need to compare your table with all other possible tables. You could do it for other table sizes, but only for very small n, because combinations easily surpass any computer's capacity.

You can find an example in:

Statistical Methods for Rates and Proportions: Joseph L. Fleiss

Answer 3

yes you can!
go on http://vassarstats.net/
and look at the calculator for " Fisher Exact Probability Test: 2x3"