Thomas J. Madden, and Neil A. Firtle discuss the relationship between delivery time and computer-assisted ordering. A sample of 40 firms shows that 16 use computer-assisted ordering, while 24 do not. Furthermore, past data are used to categorize each firm's delivery times as below the industry average, equal to the industry average, or above the industry average. The results obtained are given in Table 12.7.
TABLE 12.7
A Contingency Table Relating Delivery Time and Computer-Assisted Ordering

a. Test the hypothesis that delivery time performance is independent of whether computer-assisted ordering is used. What do you conclude by setting α = .05?
b. Verify that a chi-square test is appropriate.
c. Is there a difference between delivery-time performance between firms using computer assisted ordering and those not using computer-assisted ordering?
d. Carry out graphical analysis to investigate the relationship between delivery-time performance and computer-assisted ordering. Describe the relationship.

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Delivery Time Below Industry Average Above Industry Average Computer- Assisted Ordering No Yes Column total Equal to Industry Average 12 Row Total 24 16 40 4 10 14 8 4 16 10