A Confirmatory Factor Analytic Study Examining the Dimensionality of Educational Achievement Tests

It is important to check the fundamental assumption of most popular Item Response Theory models, unidimensionality. However, it is hard for educational and psychological tests to be strictly unidimensional. The tests studied in this paper are from a standardized high-stake testing program. They feature potential multidimensionality by presenting various item types and item sets. Confirmatory factor analyses with one-factor and bifactor models, and based on both linear structural equation modeling approach and nonlinear IRT approach were conducted. The competing models were compared and the implications of the bifactor model for checking essential unidimensionality were discussed.

Measuring Middle School Achievement Growth With Student Growth Percentile Methodology

This study examined reading and mathematics achievement growth for middle school students over three years using statewide test scores using student growth percentile methodology (Betebenner, 2008). This newly-emerging growth methodology provides a basis for examining growth normatively (“what is”) in order to provide a foundation for policies about adequate growth (“what should be”) and excellent growth (“what could be”). Growth is compared among student subgroups and different middle schools. A particular focus of the study is identifying typical growth trajectories of low-achieving 6th graders through the middle school years.