[1] Stanford Univ, Dept Stat, Stanford, CA 02135 USA
[2] Rutgers State Univ, Dept Stat, Piscataway, NJ 08854 USA
[3] Univ Penn, Dept Stat & Data Sci, Philadelphia, PA 19104 USA
[4] Univ Penn, Perelman Sch Med, Dept Biostat Epidemiol & Informat, Philadelphia, PA 19104 USA