DEVELOPING A COMMON METRIC IN ITEM RESPONSE THEORY

Abstract

A common problem arises when independent estimates 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 vertical equating and in studies of item bias. This paper discusses a number of methods for transforming one metric to another metric and presents a new method. Data are given comparing this new method with a current method and recommendations are made.