Range of Values of Cohen's Kappa Statistic

Theorem

Let $D$ be a set of observations which are independently classified by two observers $A$ and $B$.

Let $\kappa$ denote Cohen's kappa statistic over a set of observations.

Then:

$-1 \le \kappa \le 1$

where:

$1$ indicates total agreement between $A$ and $B$

$0$ indicates a level of agreement determined completely by chance

$-1$ indicates apparent disagreement between $A$ and $B$.

Proof

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Sources

• 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): Cohen's kappa statistic