8.86 How often feel sad? Refer to the previous exercise.

This question was asked of 10 students in a class at the University of Wisconsin recently. The responses were 0, 0, 1, 0, 7, 2, 1, 0, 0, 3.

Find and interpret a 90% confidence interval for the population mean and indicate what you would have to assume for this inference to apply to the population of all University of Wisconsin students.