extended · article · 2025

On Specific Objectivity and Measurement by Rasch Models: A Statistical Viewpoint

Svend Kreiner; Ivor W. Molenaar

Rasch's original definition of specific objectivity insisted that measurement by items of educational tests had to be provided by estimates of person parameters of a measurement model that did not involve estimates of item parameters.It was never stated clearly, but there is no doubt that Rasch was thinking about conditional maximum likelihood (CML) estimates similar to the well-known CML estimates of item parameters.However, for technical reasons, there are only few examples of attempts to implement the CML estimates of person parameters in software applications for item analysis by Rasch models.Nevertheless, today CML estimation of person parameters in Rasch models is possible.And since the exact distribution of estimates of person parameters in Rasch models is known, it is possible to compare the performance of the specific objective CML estimates of person parameters to the performan...