In a random sample of 8 ​people, the mean commute time to work was 33.5 minutes and the standard deviation was 7.4 minutes. A 90​% confidence interval using the​ t-distribution was calculated to be left parenthesis 28.5 comma 38.5 right parenthesis. After researching commute times to​ work, it was found that the population standard deviation is 9.6 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.
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Part 1
The margin of error of mu is
  
5.58.
​(Round to two decimal places as​ needed.)
Part 2
A 90​% confidence interval using the standard normal distribution is left parenthesis nothing comma nothing right parenthesis .
  
  
​(Round to one decimal place as​ needed.)