In an effort to investigate the premium charged by insurance companies for auto insur- ance, an agency randomly selects a few drivers who are insured by one of three different companies. These individuals have similar cars, driving records, and levels of coverage.
Table gives the premiums paid per 6 months by these drivers with these three companies.
|
Table
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|
|
Company I
|
Company II
|
Company III
|
|
396
|
348
|
378
|
|
438
|
360
|
330
|
|
336
|
522
|
294
|
|
318
|
474
|
432
|
(a) Construct an analysis-of-variance table and interpret the results.
(b) Using the 5% signi?cance level, test the null hypothesis that the mean auto insurance premium paid per 6 months by all drivers insured for each of these companies is the same. Assume that the conditions of completely randomized design are met.