4. To investigate whether age is associated with the incidence of nosocomial angina among elderly patients with coronary heart disease after receiving noncardiac surgery, 1500 patients aged over 60 years who underwent noncardiac surgery were enrolled. The incidence of postoperative nosocomial angina in patients of different ages is summarized in Table 11.20.

Please answer the following questions:

(a) What is the appropriate method in testing the difference of postoperative nosocomial angina in different age groups? Please state H0 and H1 .

(b) Please test the hypothesis and interpret the result.

(c) What is the requirement for conducting a χ2 test for this 3×2 contingency table? Is the requirement the same as for the 2×2 contingency table?

(d) Is it appropriate to conclude that the incidence of postoperative nosocomial angina increases with age?