Suppose that you are analyzing one of the hundreds of statistical studies that link smoking with lung cancer.

The study analyzed thousands of randomly selected people, some of whom had lung cancer.

The statistics indicate that those who have lung cancer smoked on average significantly more than those who did not have lung cancer.

a. Explain how you know that the data are observational.

b. Is there another interpretation of the statistics besides the obvious one that smoking causes lung cancer? If so, what is it? (Students who produce the best answers will be eligible for a job in the public relations department of a tobacco company.)

c. Is it possible to conduct a controlled experiment to produce data that address the question of the relationship between smoking and lung cancer?

If so, describe the experiment.