Alexander von Eye is Professor Emeritus of Psychology at the Department of Psychology at Michigan State University in East Lansing, MI, USA. His primary research interests include the development and application of methods for the analysis of categorical and longitudinal data, computer simulations, and developmental research. He is also concerned with the theory of person-oriented research and with the development of methods for causal research. He has published numerous books, mostly on topics of applied statistics, and he is the author of over 400 articles in scholarly journals.Wolfgang Wiedermann is an Associate Professor of Quantitative Methods at the Department of Educational, School & Counseling Psychology and the Missouri Prevention Science Institute at the University of Missouri, Columbia, MO, USA. His primary research interests include the development of methods for causal inference, methods to determine the direction of causal dependence, andmethods for person-oriented research settings. He has edited books on statistical methods for causal inference and new developments in statistical methods for dependent data analysis in the social and behavioral sciences.