Invariance, Artifact, and the Psychological Setting of Rasch's Model: Comments on Engelhard

摘要

In the following, I confine my comments mainly to the issue of invariance in relation to Rasch's model for dichotomous, ability test items. It is senseless to seek in the logical process of mathematical elaboration a psychologically significant precision that was not present in the psychological setting of the problem. (Boring, 1920) Invariance is an important concept, yet all measurements lack it. Invariance is a relative concept and a matter of degree. Scientists want measurements providing knowledge of the things measured that are free of artifactual influences. However, because all measurements involve such influences, measures are never absolutely invariant. Well-known artifacts are the choice of unit and the choice of a relation of additivity. This is well illustrated in Rasch's model.