Nan Kong

A Unified Approach to Linear Equating for the Nonequivalent Groups Design

This article describes a new, unified framework for linear equating in a non-equivalent groups anchor test (NEAT) design. The authors focus on three methods for linear equating in the NEAT design—Tucker, Levine observed-score, and chain—and develop a common parameterization that shows that each particular equating method is a special case of the linear equating function in the NEAT design. A new concept, the method function, is used to distinguish among the linear equating functions, in general, and among the three equating methods, in particular. This approach leads to a general formula for the standard error of equating for all linear equating functions in the NEAT design. A new tool, the standard error of equating difference, is presented to investigate if the observed difference in the equating functions is statistically significant.