Effects of smoking on sleep is studied by collecting samples from a group of smokers and a group of non-smokers. The time (minutes) that it takes to fall asleep is measured for both groups and the data is as follows: Non-smokers: 27.4 25.9 26.2 34.7 29.6 28.2 40.3 30 30.6 31.6 47.1 19.8 35.8 37.4 12.9 Smokers: 52.1 22.1 47.6 53.1 45.0 51.7 36 61.1 43.8 23.7 14.8 a) Find the 95% confidence interval for the difference between the means, assuming normal populations with equal variances. b) What does the confidence interval reveal about smoking?