19. For the data in the Excel file Grade Point Averages, find 90%, 95%, and 99% confidence intervals for the mean GPA. Compute the confidence intervals using the appropriate formulas and verify your results using the Excel Confidence Intervals template.

36. For the data in the Excel file Education and Income, find 95% confidence intervals for the mean annual income of males and the mean annual income of females. Can you conclude that the mean income of one group is larger than the other?

39. Using the data in the worksheet Consumer Transportation Survey, develop 95% and 99% prediction intervals for the following: a. the hours per week that an individual will spend in his or her vehicle b. the number of miles driven per week