The Rasch model from the perspective of the representational theory of measurement

Representational measurement theory is the dominant theory of measurement within the philosophy of science; and the area in which the theory of conjoint measurement was developed. For many years it has been argued the Rasch model is conjoint measurement by several psychometricians. This paper critiques this argument from the perspective of representational measurement theory. It concludes that the Rasch model is not conjoint measurement as the model does not demonstrate the existence of a representation theorem between an empirical relational structure and a numerical relational structure. Psychologists seriously interested in investigating traits for quantitative structure should use the theory of conjoint measurement itself rather than the Rasch model. This is not to say, however, that empirical relationships between conjoint measurement and the Rasch model are precluded. The paper concludes by suggesting some relevant research avenues.