1. Statistics Program, Computer, Electrical and Mathematical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Makkah, Kingdom of Saudi Arabia
2. Statistics and Operations Research Department, King Saud University (KSU), Riyadh 11564, Riyadh, Kingdom of Saudi Arabia
3. Department of Epidemiology and Biostatistics, Imperial College London, London, UK