Coefficients for Interrater Agreement

The degree of agreement between two raters who rate a number of objects on a certain characteristic can be expressed by means of an association coefficient (e.g., the product-moment correlation). A large number of association coeffi cients have been proposed, many of which belong to the class of Euclidean coefficients (ECs). A discussion of desirable properties of ECs demonstrates how the identity coefficient and its generalizations, which constitute a family of ECs, can be used to assess interrater agreement. This family of ECs contains coefficients for both nominal and non-nominal (ordinal and metric) data. In particular, it is pointed out which infor mation contained in the data is accounted for by the various coefficients and which information is ignored.