Susan E. Embretson is Professor Emeritus at both the University of Kansas and the Georgia Institute of Technology in the USA. She received her Ph.D. from the University of Minnesota. Her primary interest has concerned developing and applying item response theory (IRT) models for the response processes used by examinees to solve aptitude items.

Steven P. Reise received his Ph.D. from the Department of Psychology at the University of Minnesota in 1990. He is presently Professor of Psychology at UCLA in Quantitative Psychology. His research focuses on the application of item response theory (IRT) models to personality, psychopathology and health outcomes measures. In recent years, his interests have centered on bifactor modeling and projection.