1. Seyoon Ko is Postdoctoral Scholar, Department of Biostatistics, UCLA Fielding School of Public Health, Los Angeles, California 90095, USA
2. Hua Zhou is Professor, Department of Biostatistics, UCLA Fielding School of Public Health, Los Angeles, California 90095, USA
3. Jin J. Zhou is Associate Professor, Department of Medicine, UCLA David Geffen School of Medicine, Los Angeles, California 90095, USA, and Department of Epidemiology and Biostatistics, Mel and Enid Zuckerman College of Public Health, University of Ari
4. Joong-Ho Won is Associate Professor, Department of Statistics, Seoul National University, Seoul, Korea