1. MIT Sloan School of Management and Operations Research Center, Massachusetts Institute of Technology, Cambridge, MA
2. Department of Statistics, The Wharton School, University of Pennsylvania, Philadelphia, PA
3. Center for Clinical Epidemiology and Biostatistics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA
4. Division of Pulmonary and Critical Care Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA