A longitudinal study of occupational status and smoking behavior among women reported at baseline that 170 per 1000 professional/managerial women were nicotine dependent. The corresponding rate among blue collar women was 310 per 1000. At the a = 0.05 level, determine whether there is a significant difference in nicotine dependence between the proportion of women who are classified as professional/managerial workers in comparison to those who are classified as blue collar workers. Then compute the approximate 99% confidence interval for the difference between these two proportions.