Question: Last month a large national bank s average payment time was
Last month, a large national bank’s average payment time was 33 days with a standard deviation of 4 days. This month, the average payment time was 33.5 days with a standard deviation of 4 days. They had 1,000 customers both months.
a. Build a 95% confidence interval on the difference between this month’s and last month’s payment times. Is there evidence that payment times are increasing?
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