He has his Ph.D. from the Quantitative Methods in Education program at University of Minnesota. His research has been primarily concerned with statistical modeling of multivariate longitudinal/repeated measures data. Recent work has been on Nonlinear Mixed Effects Mixture (NLMM) models, which cluster individuals based on characteristics of their growth trajectories and hence represent the confluence of nonlinear mixed effects models and finite mixture models. These methods extend current linear mixture model methodology to include intrinsically nonlinear functions, and also may be extended to latent classes.