Document Type : Research Articles
1 Department of Biostatistics, Faculty of Paramedical Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
2 Department of Epidemiology and Biostatistics, school of public health, Hamadan University of Medical science, Hamadan, Iran.
3 Department of Medical Science, Iran Universitf of Medical Sciencesy, Tehran, Iran.
4 Qom University of Medical Sciences, Qom, Iran.