The first step in the analysis was to see whether the distribution of medical and non-medical students varied significantly by region in the sample. Of the 980 medical students, 487 were from the north and 493 were from the south. Of the 916 non-medical students, 490 were from the north and 426 were from the south. The variation in relative proportion was insignificant across regions (p = 0.10) and the rate of current smoking was not significantly different: 29.7% in the north and 26.8% in the south (p = 0.16). The gender distribution for the two regions was also similar (62% and 59% male, respectively; p = 0.19). Since there was no geographic difference in relative proportion, smoking prevalence or gender distribution, data from the northern and southern regions were combined to simplify the analysis.