Modeling multidimensional test data with a unidimensional model can result in serious statistical errors, such as bias in item parameter estimates. Many methods exist for assessing the dimensionality of a test. The current study focused on DIMTEST. Using simulated data, the effects of sample size splitting for use with the ATFIND procedure for…

Alternatives to multidimensional scaling analysis of numerical relationship judgments in extracting information about students' knowledge were investigated. Undergraduate students completed a multiple choice test over knowledge of individual concepts, an essay test covering relationships among concepts, and a relationship judgment test that…