L. Andries van der Ark is professor by special appointment in quantitative research methods at the Research Institute of Child Development and Education of the University of Amsterdam. His research interests include reliability analysis, nonparametric item response theory, Mokken scale analysis, and marginal models for the analysis of test and questionnaire data. Marie Wiberg is professor of statistics with a specialty in psychometrics at Umeå University in Sweden. Her research interests include test equating, applied statistics, large scale assessments, and psychometrics in general. Steven A. Culpepper is associate professor of statistics at the University of Illinois at Urbana-Champaign. His research interests include statistical modeling in the social sciences, Bayesian models and computation, cognitive diagnosis, and alternative standardized testing formats. Jeffrey A. Douglas is a professor of statistics at the University of Illinois at Urbana-Champaign. He conducts research in latent variable analysis with a particular emphasis on item response models and cognitive diagnosis models with applications in educational testing. Wen-Chung Wang is chair professor of educational and psychological measurement at the Educational University of Hong Kong. His research interests include Rasch measurement, item response theory, computerized adaptive testing, diagnostic classification models, and ipsative data analysis.