A Note on Levine’s Formula for Equating Unequally Reliable Tests Using Data From the Common Item Nonequivalent Groups Design

Abstract

Levine’s formula for equating unequally reliable tests using data collected in the common item nonequivalent groups equating design is an estimate of a linear function relating true scores on two test forms to be equated. Because a function relating true scores is applied to the observed score, it is not clear how the resulting converted observed score is in any sense comparable to the observed score it is being equated to. This article demonstrates that Levine’s formula can be interpreted as a method of moments estimate of an equating function that results in first order equity of the equated test score under a classical congeneric model.