(a)A theory about grades is that the average student in a second term stats class scores an average grade of 68. It is known that the standard deviation of grades in a second term stats class is 9. A recent sample of 17 students produced an average of 74. At 95% does this provide enough evidence to refute this claim? Up to what evidence can we refute the claim

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(b) For the above problem, construct a 95% confidence interval for the average grade in a second term stats class. Discuss how this compares to the results of the test.