6. A study conducted by a commuter train transportation authority involved surveying a random sample of 400 passengers. The results show that a customer had to wait on the average 8.9 minutes with a standard deviation of 5.6 minutes to buy his or her ticket. Find the lower and upper limits of the 99% confidence interval of the true mean waiting time respectively.
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- Sample mean (\(\bar{x}\)) = 8.9 minutes - Standard deviation (\(s\)) = 5.6 minutes - Sample size (\(n\)) = 400 passengers - Confidence level = 99% The formula for the confidence interval of the mean is: \[ \bar{x} \pm z \times \frac{s}{\sqrt{n}} \] Show more…
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