Symbols:Greek/Kappa/Cohen's Kappa Statistic

Cohen's Kappa Statistic

$\kappa$

Let two observers $A$ and $B$ independently classify each of a set of observations into $2$ or more categories.

Cohen's kappa statistic $\kappa$ is a measure of agreement between $A$ and $B$.

Let there be $N$ observations.

Let $n$ denote the number of agreements over all categories.

Let $p_{\mathrm {obs} } := \dfrac n N$ be the observed proportion of agreements.

Let $p_{\mathrm {exp} }$ denote the expected proportion of agreements over all categories under random assignment, as calculated in the usual manner for a contingency table.

Then:

$\kappa = \dfrac {p_{\mathrm {obs} } - p_{\mathrm {exp} } } {1 - p_{\mathrm {exp} } }$

Its $\LaTeX$ code is \kappa .