Wood et al. (1979) studied the impact of comprehensive planning on the financial performance of banks. They used 4 random samples to perform their study. The sample size n, average annual percent return on owner’s equity X̅, and sample standard deviation s are presented in the table.

Average Annual Percent Return on Net Income

(a) Use the data in this table to construct a 90 % confidence interval for the difference between the mean of the “comprehensive formal planners” group and that of the “no formal planning system” group.

(b) Perform a hypothesis test at α = 10 %.

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Classification Comprehensive formal planners Partial formal planners No formal planning system Control group n 26 6 9 20 x% 11.928 9.972 4.936 2.098 S 3.865 7.470 4.466 10.834