Additivity and Interactions in Offense Seriousness Scales

Abstract

An issue of concern in the practical application of offense seriousness scales is that of the additive nature of separable components of criminal events. Recent attempts to verify the additivity assumption implicit in the most widely used scale have given mixed but damaging results. This report discusses additivity within the conceptual framework of interaction. In the first study reported, subjects judged the seriousness of five crime "types," each of which varied ten levels of monetary loss. Significant main effects for crime type and monetary value were observed, as was an interaction effect of crime type and monetary value. A second study replicates and extends the first. Implications for the assumption of additivity in seriousness scales are discussed.