Improving driving performance while fatigued. Refer to the Human Factors (May, 2014) study of driving performance while fatigued, Exercise 9.31 (p. 549). Recall that the researchers had 40 college students drive a long distance in a simulator. While driving, each student performed a task. One group of student-drivers performed a verbal task continuously (continuous verbal condition); another group performed the task only at the end of the drive (late verbal condition); a third group did not perform the task at all (no verbal condition); and, the fourth group listened to a program on the car radio (radio show condition). The dependent variable of interest was the percentage of billboards recalled by the student-driver. The data are listed in the table below. Continuous Verbal Late Verbal No Verbal Radio Show 14 57 64 37 63 64 83 45 10 66 54 87 29 18 59 62 37 95 60 14 60 52 39 46 43 58 56 59 4 92 73 45 36 85 78 45 47 47 73 50

a. Write a model for mean recall percentage, E1y2, as a function of task group (continuous verbal, late verbal, no verbal, and radio show). Use radio show as the base level for the qualitative independent variable, task group.

b. Measures of central tendency for the recall percentage measurements of each task group are displayed in the accompanying Minitab printout. Use this information to estimate the b parameters of the model, part

a. c. Fit the model, part

a, to the data in the file. Use the output to verify your b estimates in part

b. d. Refer to the output, part

c. Conduct a test 1at a = .012 to determine if the mean recall percentage differs for student-drivers in the four groups. Your answer should agree with that of Exercise 9.31. Applying the Concepts—Advanced