Llewellyn J. Cornelius, PhD, LCSW is a professor at the University of Maryland School of Social Work. Dr. Cornelius has more 30 years of experience in survey and evaluation research, including supervising students in the development, pilot testing and fielding of surveys. He is currently on the National Committee on Vital and Health Statistics, a committee of research scientists who advise the Secretary of USDHHS regarding the design and management of all federal health surveys. Donna Harrington, PhD, is Professor and Associate Dean for Doctoral and Post-Doctoral Education at the University of Maryland School of Social Work. Dr. Harrington teaches PhD courses in advanced data analysis techniques, including structural equation and multi-level modeling, and the integration of research and theory. Dr. Harrington's recent research focuses on measurement issues such as the validation of translated measures and testing the validity and reliability of measures for diverse populations. Dr. Harrington wrote Confirmatory Factor Analysis (2009) for the Oxford University Press Pocket Guides to Social Work Research Methods series.