The following table (compiled from police reports) shows the record of automobile accidents for three age groups over the last year in a five- county region.
Number of Drivers Having:
|
Age 17-30
|
No Accidents
90,243
|
1 Accident
12,050
|
2 or > Accidents
1,822
|
|
Age 31-55
|
243,125
|
21,443
|
2,822
|
|
Over 55
|
149,674
|
16,621
|
2,293
|
a. An analyst points out that of 57,051 drivers involved in accidents last year, drivers aged 31 to 55 accounted for 24,265 cases, or some 43 percent of the total-a far greater proportion than any other age group. Should one conclude that this age group has the highest-risk drivers?
b. Which age group has the worst accident record? The best? Explain.
c. A separate analysis shows that for drivers aged 35 to 45, the rate of accidents (one or more per year) is 9.3 per 1,000 drivers. For drivers aged 65 to 75, the rate is 8.4 per 1,000 drivers. However, most studies show that members in the younger group are much safer drivers than those in the older group. Why might a simple comparison of accident rates per driver be misleading? What other important factor should be taken into account?