Refer to Table D.12 of the Data Bank. The responses, of persons in the first and second age groups, on the frequency of credit card use question, have the summary statistics

(a) Obtain a 98% confidence interval for the difference in the two population mean frequency of credit card use scores.
(b) Test for equality of the two means versus a two-sided alternative. Use a = .02.

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Age 19-24 18 3.000 .609 25-34 28 4.429 643