Behavioral researchers have developed an index designed to measure managerial success. The index (measured on a 100-point scale) is based on the manager’s length of time in the organization and his or her level within the firm; the higher the index, the more successful the manager. Suppose a researcher wants to compare the average success index for two groups of managers at a large manufacturing plant. Managers in group 1 engage in a high volume of interactions with people outside the manager’s work unit. (Such interactions include phone and face-to-face meetings with customers and suppliers, outside meetings, and public relations work.) Managers in group 2 rarely interact with people outside their work unit. Independent random samples of 12 and 15 managers are selected from groups 1 and 2, respectively, and the success index of each is recorded. The results of the study are given in Table 8.2.

a. Use the data in the table to estimate the true mean difference between the success indexes of managers in the two groups. Use a 95% confidence interval.

b. Interpret the interval, part a.

c. What assumptions must be made so that the estimate is valid? Are they reasonably satisfied?

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Table 8.2 Managerial Success Indexes for Two Groups of Managers Group 1 Group 2 Interaction with Outsiders Few Interactions 34 68 65 66 58 70 78 53 60 71 68 63 69 63 62 42 52 53 57 53 36 46 43 56 48 50 42