1. Department of Biostatistics, School of Health, Mashhad University of Medical Sciences, Mashhad, Iran
2. Orthopedic Research Center, Mazandaran University of Medical Sciences, Sari, Iran
3. Department of Statistics, Faculty of Mathematical Sciences, Ferdowsi University of Mashhad, Mashhad, Iran
4. Centre for Communicable Diseases Control, Ministry of Health and Medical Education, Tehran, Iran