Second-Hand Smoke Data Set 14 “Passive and Active Smoke” includes cotinine levels measured in a group of nonsmokers exposed to tobacco smoke (n = 40, x = 60.58 ng>mL, s = 138.09 ng>mL) and a group of nonsmokers not exposed to tobacco smoke (n = 40, x = 16.35 ng>mL, s = 62.53 ng>mL). Cotinine is a metabolite of nicotine, meaning that when nicotine is absorbed by the body, cotinine is produced.

a. Use a 0.05 significance level to test the claim that nonsmokers exposed to tobacco smoke have a higher mean cotinine level than nonsmokers not exposed to tobacco smoke.

b. Construct the confidence interval appropriate for the hypothesis test in part (a).

c. What do you conclude about the effects of second-hand smoke?