In a random sample of 8 ​people, the mean commute time to work was 35.5 minutes and the standard deviation was 7.2 minutes. A 90​% confidence interval using the​ t-distribution was calculated to be...

In a random sample of 8 ​people, the mean commute time to work was 35.5 minutes and the standard deviation was 7.2 minutes. A 90​% confidence interval using the​ t-distribution was calculated to be (30.7,40.3). After researching commute times to​ work, it was found that the population standard deviation is 9.1 minutes. Find the margin of error and construct a 90​% confidence interval using the standard normal distribution with the appropriate calculations for a standard deviation that is known. Compare the results.