Developing a Common Metric in Item Response Theory

Abstract

A common problem arises when independent esti mates of item parameters from two separate data sets must be expressed in the same metric. This problem is frequently confronted in studies of horizontal and ver tical equating and in studies of item bias. This paper discusses a number of methods for finding the appro priate transformation from one metric to another met ric and presents a new method. Data are given com paring this new method with a current method, and recommendations are made.