Refer to Grade point average Problem 1.19. a. Obtain a 95 percent interval estimate of the mean freshman GPA for students whose ACT test score is 28. Interpret your confidence interval: b. Mary Jones obtained a score of 28 on the entrance test Predict her freshman GPA using a 95 percent prediction interval. Interpret your prediction interval: c. Is the prediction interval in part (b) wider than the confidence interval in part (a)? Should it be? d. Determine the boundary values of the 95 percent confidence band for the regression line when Xh 28. Is your confidence band wider at this point than the confidence interval in part (a)? Should it be?