The purpose of this paper is to present a generalization of the concept of item difficulty to test items that measure more than one dimension. Three common definitions of item difficulty were considered: the proportion of correct responses for a group of individuals; the probability of a correct response to an item for a specific person; and the…

Summarizes the current state of the art in test construction and contrasts it with previous conceptual models, some of which are wrong or misleading. New methodologies for item selection and review are presented, with current thinking on the specification of technical characteristics of tests. (Author/SLD)