Remember when I asked you for your age on the first day of class? Well, here is the data I obtained: 18, 18, 18, 18, 18, 19, 19, 20, 20, 20, 20, 20, 20, 21, 21, 21, 22, 22, 22, 23, 24, 24, 24, 24, 25, 25, 25, 26, 29, 31, 32, 40, 41, 49

Calculate the proportion of students in the sample who can buy recreational drugs in Oregon (aged 21 or over). Use this to find a 90% confidence interval for the true proportion of intro-stats students who can buy recreational drugs.