Psychometric Scale in Modeling Developmental Processes and Ecological Factors

of talk conference on Modeling Developmental Processes in Ecological Context in Tempe, Arizona – March 2004 Susan E. Embretson University of Kansas Psychometric scales can influence assessments of relationships between ecological factors and developmental processes. Outcome measures for developmental studies on psychological traits are typically based on raw scores (or their linear transformations) from a fixed content test. In this presentation, simulations based on item response theory (IRT) are presented to show the impact of test properties on 1) comparisons between groups that differ in ecological factors, 2) comparison of cross-sectional growth curves, 3) comparison of change between groups and 4) the regression of outcome on age and ecological factors. In summary, the magnitude of impact depends on the appropriateness of test difficulty level. Simulation results are also presented to show that optimal measurement from adaptive testing, rather than IRT scaling alone, is required to adjust these effects. An application to a study on agerelated changes in spatial ability is then given to illustrate the impact.