Fisher's exact test for a 2x2 table

Command:

Tests Fisher's exact test

Description

Fisher's exact test in the Tests menu is used to calculate an exact P-value for a 2x2 frequency table with small number of expected frequencies, for which the Chi-squared test is not appropriate.

Required input

The data (representing number of cases) for the 2x2 table are entered in the dialog box.

Example: treatment A resulted in 6 successes and 1 failure (6/7 = 85.7%) whereas treatment B resulted in 2 success and 8 failures (2/10 = 20%). The following is entered in the dialog box:

Click Test.

Results

MedCalc calculates the exact P-value, which is the probability of obtaining the observed result or a more extreme result.

In the example, the result is P=0.015 which indicates that the 2 treatments gave significantly different results.

In an optional Comment input field you can enter a comment or conclusion that will be included on the printed report.

Literature

• Altman DG (1991) Practical statistics for medical research. London: Chapman and Hall.

See also

• Fisher's exact test online calculator.

• Fisher's exact test on Wikipedia.