Three different brands of tires were compared for wear characteristics. From each brand of tire, ten tires were randomly selected and subjected to standard wear-testing procedures. The average mileage obtained for each brand of tire and sample variances (both in 1,000 miles) are shown below.
| Brand A | Brand B | Brand C |
Average Mileage | 37 | 38 | 33 |
Sample Variance | 3 | 4 | 2 |
At 95% confidence, test to see if there is a significant difference in the average mileage of the three brands.