Anational center for smoking and lung obstruction health statistics data brief published in 2015 (nr. 181) looked at the association between lung obstruction and smoking status in adults 40 to 79 years old. in a random sample of 6927 adults without any lung obstruction, 54.1% never smoked. in a random sample of 1146 adults with lung obstruction (such as asthma or copd), 23.8% never smoked. 10.4 a. find and interpret a point estimate of the difference between the proportion of adults without and with lu obstruction who never smoked b. a 99% confidence interval for the true difference is (0.267, 0.339). interpret. c. what assumptions must you make for the interval it part b to be valid?