Students Philip Hurst and Yuan Chao Jiang investigated the accuracy of three different brands of .22 caliber ammunition at two different distances. The brands were Remington, Winchester, and Federal, and the two designated distances were 25 and 50 yards. “Accuracy” was measured by distance from the bull’s-eye, in centimeters. All bullets were shot from the same rifle, and the order of the bullets was randomized. The accompanying table shows the mean accuracy at each combination based on K = 75 bullets.

a. Identify the factors, levels, and treatments in this experiment.
b. Create an interaction plot for the accuracy data, and comment on what you see.
c. From software, SS(Dist.) = 568.97, SS(Brand) = 2.97, SS(Dist.*Brand) = 2.48, and SSE = 1041.49. Test for the presence of main and interaction effects for the accuracy data at the α = .05 level. Are the results consistent with your interaction plot?

Transcribed Image Text:

25 Firing distance 50 Fed. 3.027 5.440 Bullet brand Rem. 3.360 5.413 Win. 3.280 5.560