A smoking researcher is interested in estimating the average age when cigarette smokers first began to smoke.

Question:

A smoking researcher is interested in estimating the average age when cigarette smokers first began to smoke. Taking a random sample of 25 smokers, she determines a sample mean of 16.8 years and a sample standard deviation of 1.5 years. Construct a 95% confidence interval to estimate the population mean age of the onset of smoking.