Some days of the week are more dangerous than others, according to Traf?c Safety Facts produced by the National Highway Traf?c 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 possible reason for the change?