38. In an experiment to see whether the amount of coverage of light-blue interior latex paint depends either on the brand of paint or on the brand of roller used, 1 gallon of each of four brands of paint was applied using each of three brands of roller, resulting in the following data (number of square feet covered).

Roller Brand 1 2 3 1 454 446 451 Paint 2 446 444 447 Brand 3 439 442 444 4 444 437 443

a. Construct the ANOVA table. [Hint: The computations can be expedited by subtracting 400 (or any other convenient number) from each observation.

This does not affect the nal results.]

b. State and test hypotheses appropriate for deciding whether paint brand has any effect on coverage.

Use a  .05.

c. Repeat part

(b) for brand of roller.

d. Use Tukey s method to identify signi cant differences among brands. Is there one brand that seems clearly preferable to the others?

e. Check the normality and constant variance assumptions graphically.