This is a continuation of Exercise 20 in Chapter 12. A case-control study in Berlin, reported by Kohlmeier et al. (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. State the null and alternative hypotheses for this situation.
b. Construct a contingency table for the data.
c. Calculate the expected counts.
d. Calculate the value of the chi-square statistic.
e. Make a conclusion about statistical signifi­cance using a level of 0.05. State the conclusion in the context of this situation.