1. School of Medical Statistics and Biometry, Department of Interdisciplinary Medicine, University of Bari Aldo Moro, 70124 Bari, Italy
2. School of Medical Statistics and Biometry, University of Bari Aldo Moro, Azienda Sanitaria Locale Taranto, 74121 Taranto, Italy
3. Unit of Statistics and Epidemiology, Azienda Sanitaria Locale Taranto, 74121 Taranto, Italy
4. Department of Interdisciplinary Medicine, University of Bari Aldo Moro, 70124 Bari, Italy