On Agreement Tables with Constant Kappa Values

Kappa coefficients are standard tools for summarizing the information in cross-classifications of two categorical variables with identical categories, here called agreement tables. When two categories are combined the kappa value usually either increases or decreases. There is a class of agreement tables for which the value of Cohen’s kappa remains constant when two categories are combined. It is shown that for this class of tables all special cases of symmetric kappa coincide and that the value of symmetric kappa is not affected by any partitioning of the categories.