The Kappa Statistic: A Second Look

This squib discusses the assumptions underlying different computations of the expected agreement component of the kappa coefficient of agreement and discusses how prevalence and bias affect the measure.

Abstract

In recent years, the kappa coefficient of agreement has become the de facto standard for evaluating intercoder agreement for tagging tasks. In this squib, we highlight issues that affect κ and that the community has largely neglected. First, we discuss the assumptions underlying different computations of the expected agreement component of κ. Second, we discuss how prevalence and bias affect the κ measure.