The measure of the relationship between two qualitative (non-measurable) features X and Y when the data is presented in the form of a contingency table. It is only used for tables of 2 by 2 dimension . The value of the coefficient belongs to the interval [-1,1]. The coefficient sign does not indicate the direction of dependency, because its value depends on the array structure. The absolute value closer to unity means the stronger relationship between the characteristics.

• Table of correlation
• Table of independence