30. In exercise 9, an estimated regression equation was developed relating the percentage of stu- dents who attend a four-year college to the average class size and the combined SAT score.

a. Develop a 95% confidence interval for the mean percentage of students who attend a four-year college for a school district that has an average class size of 25 and whose students have a combined SAT score of 1000.

b. Suppose that a school district in Conway, South Carolina, has an average class size of 25 and a combined SAT score of 950. Develop a 95% prediction interval for the per- centage of students who attend a four-year college.