15. A case-control study in Berlin, reported by Kohlmeier, Arminger, Bartolomeycik, Bellach, Rehm, and Thamm (1992) and by Hand et al. (1994), asked 239 lung cancer patients and 429 controls (matched to the cases by age and sex)

whether they had kept a pet bird during adulthood. Of the 239 lung cancer cases, 98 said yes. Of the 429 controls, 101 said yes.

a. Construct a contingency table for the data.

b. Compute the risk of lung cancer for bird and non-bird owners for this study.

c. Can the risks of lung cancer for the two groups, computed in part

b, be used as baseline risks for the populations of bird and non-bird owners? Explain.

d. How much more likely is lung cancer for bird owners than for non-bird owners in this study; that is, what is the increased risk?

e. What information about risk would you want, in addition to the information on increased risk in part d of this problem, before you made a decision about whether to own a pet bird?