His primary research concentration is in the areas of measurement and assessment. Much of his research concentrates on advancing methodology pertaining to item response theory, differential item functioning, and computerized adaptive testing. Other research interests include fairness issues associated with high-stakes testing, legal and professional standards of educational and psychological testing, and the use of high-stakes testing in educational accountability systems. His research has appeared in journals, such as the Journal of Educational Measurement, Applied Psychological Measurement, Educational and Psychological Measurement, Applied Measurement in Education, Psychological Methods, and Educational Measurement: Issues and Practice.