A consumer research firm wants to compare three brands of radial tires (X,Y,and Z) in terms of tread life ofer different road suffaces. Random samples of four tires of each brand are selected for each of three surfaces (asphalt, concrete, gravel). A machine that can simulate road conditions for each of the road surfaces is used to find the tread life (in thousands of miles) of each tire. Construct an ANOVA table and conduct F-tests for the presence of nonzero brand effects, road surface effects, and interaction effects. Use Alpha 0.05.
| Surface/ Brand |
X |
Y |
Z |
| Asphalt |
36,39,39,38 |
42,40,39,42 |
32,36,35,34 |
| Concrete |
38,40,41,40 |
42,45,48,47 |
37,33,33,34 |
| Gravel |
34,32,34,35 |
34,34,30,31 |
36,35,35,33 |