A researcher predicts that smoking cigarettes decreases a person's sense of smell. On a test of olfactory sensitivity, the population mean for nonsmokers is 18. A sample of 12 people who smoke a pack a day produces a mean of 16 with estimated population variance of 4.75.

a) Test the researcher's hypothesis using all 6 steps of hypothesis testing. Be sure to number all 6 steps and show all of your work.

b) IF APPROPRIATE, compute the confidence interval.

You must show all steps of hypothesis testing and all calculations in order to receive credit.