Heart disease and smoking. In a study of heart disease in male federal employees, researchers classified 356 volunteer subjects according to their socioeconomic status (SES) and their smoking habits. There were three categories of SES: high, middle, and low. Individuals were asked whether they were current smokers, former smokers, or had never smoked. Here are the data, as a two-way table of counts
Smoking behavior is stored numerically as 1, 2, or 3 as given in the column headings above.
(a) Higher-SES people in the United States smoke less as a group than lower-SES people. Do these data show a relationship of this kind? Give percents that back your statements.
(b) Apply the chi-square test to see if there is a significant relationship between SES and smoking behavior.
(c) The chi-square test ignores the ordering of the responses. Use the Kruskal-Wallis test (with many ties) to test the hypothesis that some SES classes smoke systematically more than others.