Donald R. Cooper and C. William Emory discuss studying the relationship between on-the-job accidents and smoking. Cooper and Emory describe the study as follows:
Suppose a manager implementing a smoke-free workplace policy is interested in whether smoking affects worker accidents. Since the company has complete reports of on-the-job accidents, she draws a sample of names of workers who were involved in accidents during the last year. A similar sample from among workers who had no reported accidents in the last year is drawn. She interviews members of both groups to determine if they are smokers or not.
The sample results are given in Table 12.6.
TABLE 12.6
A Contingency Table of the Results of the Accidents Study

a. For each row and column total in Table 12.6, find the corresponding row/column percentage,
b. For each cell in Table 12.6, find the corresponding cell, row, and column percentages.
c. Use the MINITAB output in Figure 12.4 to test the hypothesis that the incidence of on-the-job accidents is independent of smoking habits. Set α = .01.
FIGURE 12.4
MINITAB Output of a Chi-Square Test for Independence in the Accident Study

d. Is there a difference in on-the-job accident occurrences between smokers and nonsmokers? Explain.

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On-the-Job Accident Yes 12 Row Total 16 15 35 No 4 Smoker Heavy Moderate Nonsmoker Column total 13 34 32 Expected counts are below observed counts Accident No Accident Total 16 12 8.24 Heavy 7.76 Moderate 15 7.73 7.27 Non smoker 13 35 18.03 34 Chi-Sq# 6.860, DF 16.97 32 P-value Total 2, 0.032