Purchasing organizations such as the National Association of Purchasing Management advocate ethical purchasing practices for purchasing managers including the avoidance of situations that might influence or appear to influence purchasing decisions. In Mexico, the U.S.'s third largest trading partner, purchasing has not fully evolved into a profession with its own standards of ethical behavior. Researchers at Xavier University investigated the question: Do American and Mexican purchasing managers perceive ethical situations differently (Industrial Marketing Management, July 1999)? As part of their study, 15 Mexican purchasing managers and 15 American purchasing managers were asked to consider different ethical situations and respond on a 100-point scale with end points "strongly disagree" (1) and "strongly agree" (100). For the situation "accepting free trips from salespeople is okay." the responses shown in the table on p. 391 were obtained.

a. Consider a Wilcoxon rank sum test to determine whether American and Mexican purchasing managers perceive the given ethical situation differently.

A STATISTIX printout of the analysis is also shown on p. 391.Verify the rank sums shown on the printout are accurate.

b. Conduct the test of a = .05. Use the p-value shown on the printout to make your conclusion. (Note:

STATISTIX cmploys the equivalent Mann-Whitney U-test to analyze the data. The p-values of the two tests are identical.)

c. Under what circumstances could the two-sample t-test of Section 7.1 be uscd to analyze the data?

Check to see whether the t-test is appropriate in this situation.