1-Fifty students are enrolled in an Economics class. After the first examination, a random sample of 5 papers was selected. The grades were 60, 75, 80, 70, and 90.

a.

Provide a 90% confidence interval for the mean grade of all the students in the class. What assumption do you need to make to calculate the interval?

b.

If there were 200 students in the class, what would be the 90% confidence interval for the mean grade of all the students in the class?

please give detailed explanation