Automobile insurance is much more expensive for teenage drivers than for older drivers. To justify this cost difference, insurance companies claim that the younger drivers are much more likely to be involved in costly accidents. To test this claim, a researcher obtains information about registered drivers from the department of motor vehicles (DMV) and selects a sample of n=300 accident reports from the police department. The DMV reports the percentage of registered drivers in each age category as follows: 16% are younger than age 20; 28% are 20 to 29years old; and 56% are age 30 or older. The number of accident reports for each age group is as follows:
under age 20 Age 20-29 Age 30 or older
68 92 140
a. Does the data indicate that the distribution of accidents for the three age groups is significantly different from the distribution of drivers? Test with ox=.05.
b. Write a sentence demonstrating how the outcome of the hypothesis test would appear in a research report.