Many-faceted Rasch calibration of a gross motor instrument.

The purpose of this study was to recalibrate a well-developed motor development instrument (Ulrich, 1985) using the many-faceted Rasch model and to examine its advantages and application potential. The instrument was administered to a total of 909 children from a national multistage sampling across 9 states. These children included 451 boys and 458 girls ranging in age from 3-10 years. The instrument was recalibrated using the many-faceted Rasch model with 8 defined facets. The primary advantages of the many-faceted Rasch calibration are (a) that estimations of parameters are independent of both the examinees and testing items employed, (b) that all facets involved in the calibration can be taken into account, (c) that the calibrated facets share the same metric, and (d) that the measurement scales are additive. These advantages, together with goodness-of-fit statistics generated from the calibration, provided a convenient way to examine the appropriateness of the testing items and related facets and to determine examinees' strengths and weaknesses of their measured ability. Finally, through a step-by-step example, it was shown that applying the many-faceted Rasch calibrated instrument can be both simple and practical.