How useful is comparative judgement of item difficulty for standard maintaining?

Abstract

This article reviews the evidence on the extent to which experts' perceptions of item difficulties, captured using comparative judgement, can predict empirical item difficulties. This evidence is drawn from existing published studies on this topic and also from statistical analysis of data held by Cambridge Assessment. Having reviewed the evidence, the article then proposes a simple mechanism by which such judgements can be used to equate different tests, and evaluates the likely accuracy of the method.