Walter W. Stroup, Ph.D., is currently professor in the Department of Statistics at the University of Nebraska. His responsibilities include teaching statistical modeling, design of experiments, and research applications of mixed models in collaboration with researchers in agriculture, natural resources, medical and pharmaceutical sciences, education, and the behavioral sciences. Dr. Stroup received a B.A. degree in psychology from Antioch College, and M.S. and Ph.D. degrees in statistics from the University of Kentucky. He is widely published in statistical and applied journals and has participated in a number of symposia on issues in statistical consulting and statistical modeling. He has taught numerous short courses and workshops on generalized linear mixed models. A SAS user since 1975, Dr. Stroup is coauthor of SAS for Linear Models, Fourth Edition, SAS for Mixed Models, both editions. In additional, Dr. Stroup is author of Generalized Linear Mixed Models: Modern Concepts, Methods and Applications, an introduction to GLMMs that makes extensive use of SAS examples.