My primary research interest is psychometrics and educational and psychological measurement, focusing on implementation of item-level test data analysis methodology through various modeling framework, including item response theory, multilevel modeling, and structural equation modeling. I did pioneering work on multilevel item response theory modeling, where item response data from individuals are nested with group units, such as schools. which is represented by my 2001 publication in Journal of Educational Measurement, a special issue on multilevel measurement modeling in Journal of Applied Measurement in 2005, and several book chapters on the topic, including a recent chapter in the Handbook of Advanced Multilevel Analysis (2011). Other recent interests include developing effect size measures for testlet modeling, developing reliability measures of growth trajectory for longitudinal data modeling, and Bayesian inference for complex psychometric models.
