The purpose of the present study was to examine the accuracy of indirect trait estimates, i.e., estimates of some primary trait obtained from a second measure which have been equated to the first. The California Achievement Test in Reading was the primary measure and the Prescriptive Reading Inventory was the indirect measure. Four kinds of…

Standard procedures for estimating item parameters in Item Response Theory models make no use of auxiliary information about test items, such as their format or content, or the skills they require for solution. This paper describes a framework for exploiting this information, thereby enhancing the precision and stability of item parameter…