Wednesday, 13 November 2013

Fisher's Exact Test Calculator (2 $\times$ 2 Contingency Table)

This blog post implements an online Fisher's Exact Test on a 2 by 2 contingency matrix. The method used for calculating the two-tailed probability results is to evaluate the probabilities of more extreme results in both directions, and adding these to the probability of obtaining the entered results, if their value is less than or equal to the entered results' probability.

Referring to the contingency table below, the Null Hypothesis for Fisher's Exact test is that the outcomes for Category 1 and Category 2 are broadly similar - in other words, if we divided Outcome 2 by Outcome 1 for Category 1, we would obtain a similar result to dividing Outcome 2 by Outcome 1 for Category 2. A low value of, say, the two-tailed probability (< 0.05) could be considered a significant result, rejecting the Null Hypothesis.

Please fill in the four text areas with integers greater than or equal to zero.

Outcome 1: Outcome 2:
Category 1:

Row Sum 1

Category 2:

Row Sum 2

Column Sum 1

Column Sum 2


Results pending...