A simple correlation testing technique.

Fourfold Contingency Table

A test to see if two distinct variables are linked.

        | A | A NOT |
-----------------------------
| B     | 1 | 2     |
| B NOT | 3 | 4     |
If numbers are highest in...
REGION 1 - A and B are correlated
REGION 2 - A is correlated with the absence of B
REGION 3 - B is correlated with the absence of A
REGION 4 - Absence of A is correlated with absence of B

This is related to the Chi-squared test.


Source