Some days of the week are more dangerous than others, according to Traffic Safety Facts produced by the National Highway Traffic Safety Administration.

The average number of fatalities per day for each day of the week are shown in the accompanying table.

Average Fatalities per Day

(day of the week)

Mon Tue Wed Thurs Fri Sat Sun 1978– 1982 103 101 107 116 156 201 159 1983– 1987 98 96 99 108 140 174 140 1988– 1992 97 94 97 106 139 168 135 1993– 1997 97 93 96 102 129 148 127 1998– 2002 99 96 98 104 129 149 130 Total 99 96 100 107 138 168 138

a. Using the midpoint of each year range (e.g., 1980 for the 1978– 1982 range), construct a time-series plot that shows the average fatalities over time for each day of the week. Be sure to label each line clearly as to which day of the week it represents.

b. Write a sentence or two commenting on the difference in average number of fatalities for the days of the week.

What is one possible reason for the differences?

c. Write a sentence or two commenting on the change in average number of fatalities over time. What is one pos sible reason for the change?