extended · article · 2004

Validity and assessment: a Rasch measurement perspective

Trevor G. Bond

This paper argues that the Rasch model, unlike the other models generally referred to as IRT models, and those that fall into the tradition of True Score models, encompasses a set of rigourous prescriptions for what scientific measurement would be like if it were to be achieved in the social sciences. As a direct consequence, the Rasch measurement approach to the construction and monitoring of variables is sensitive to the issues raised in Messick's (1995) broader conception of construct validity. The theory / practice dialectic (Bond & Fox, 2001) ensures that validity is foremost in the mind of those developing measures and that genuine scientific measurement is foremost in the minds of those who seek valid outcomes from assessment. Failure of invariance, such as those referred to as DIF, should alert researchers to the need to modify assessment procedures or the substantive theory unde...