A Rasch Analysis of the KeyMath-3 Diagnostic Assessment.

Effectively assessing children's academic development can help school professionals make placement decisions and prepare appropriate instructional supports. The KeyMath-3 Diagnostic Assessment (Connolly, 2008) is a widely used assessment of children's mathematical abilities; however, despite much use, the measurement properties of the KeyMath-3 DA have not been examined, aside from the development and standardization phases. The current study conducted a Rasch analysis of the Basic Concepts content area of the KeyMath-3 DA in a diverse sample of 308 young children to assess the quality of the assessment. Rasch analytic procedures examined unidimensionality, item and person fit statistics, reliability, and item hierarchy. Misfitting items were further examined, and response patterns were modified. In general, results show that the Basic Concepts subscale is a good measure of the underlying construct of young children's understanding of the basic concepts in mathematics. Implications are discussed.