Fisherextest

Fisher's Exact Probability Test.

This file performs the Fisher exact probability test for a table of frequency data cross-classified according to two categorical variables, each of which has two levels or subcategories (2x2). It is a non-parametric statistical test used to determine if there are nonrandom associations between the two categorical variables. Fisher's exact test is used to calculate an exact P-value with small number of expected frequencies, for which the Chi-square test is not appropriate (in case the total number of observations is less than 20 or the number of frequency cells are less than 5). This test is based upon the hypergeometric probability. The test was proposed in the 1934 edition of the famous Ronald Aylmer Fisher's book 'Statistical Methods for Research Workers'.

It needs to input the four frequency cells.

The output consists of the negative, positive and both P-values. [decide to use Left, Right or 2-Tail before collecting (or looking at) the data].

If user does not put any output arguments, file returns a P-value table.