4- asample of course grades for 40 statistics students showed a sample mean of 79.5. If we know 0 = 11.5, find a 90% Confidence interval for the course grade for all statistics Students.

5- a professor wants to know the mean grade of all statistics students. How large should his sample be if he wants to be 95% Confident that the sample mean is within 2 points of the true population mean? Use & from question. 9