1. Principal Research Associate, Westat, Rockville, Maryland, USA
2. Independent Consultant, Cumming, Georgia, USA
3. Professor of Education and Applied Quantitative Methods, University of Maine, Orono, Maine, USA
4. Director, School of Learning and Teaching, Professor of Education and Applied Quantitative Methods, University of Maine, Orono, Maine, USA
5. Research Scientist, Learning Sciences & Technologies, Worcester Polytechnic Institute, Worcester, Massachusetts, USA