Potential test information for multidimensional tests

Test selection in psychological assessment is guided, both explicitly and implicitly, by how informative tests are with regard to a trait of interest. Most existing formulations of test information are sensitive to subpopulation variation, with the result that test information will vary from sample to sample. Recently, measures of test information have been developed that quantify the potential informativeness of the test. These indices are defined by the properties of the test, as distinct from the properties of the sample or examinee. As of yet, however, measures of potential information have been developed only for unidimensional tests. In practice, psychological tests are often multidimensional. Furthermore, multidimensional tests are often used to estimate one specific trait among many. This study develops measures of potential test information for multidimensional tests, as well as measures of marginal potential test information---test information with regard to one trait within a multidimensional test. In Study 1, the performance of the metrics was tested in data simulated from unidimensional, first-order multidimensional, second-order, and bifactor models. In Study 2, measures of marginal and multidimensional potential test information are applied to a set of neuropsychological data collected as part of Rush University's Memory and Aging Project. In simulated data, marginal and multidimensional potential test information were sensitive to the changing dimensionality of the test. In observed neuropsychological data, five traits were identified. Verbal abilities were most closely correlated with probable dementia. Both indices of marginal potential test information identify the Mini Mental Status Exam as the best measure of that trait. More broadly, greater marginal potential test information calculated with regard to verbal abilities was associated with greater criterion validity. These measures allow for the direct comparison of two multidimensional tests that assess the same trait, facilitating test selection and improving the precision and validity of psychological assessment.