Nelson (1993) presents data on the average access times for various disk drives. The disk drives are five brands of half-height fixed drives. The performance of disk drives depends on the computer in which they are installed. The computers could only hold four disk Table 14.9: Percentage of manganese concentrations.

Operator Sample 1 2 3 4 1 0.615 0.620 0.600 0.600 2 0.635 0.635 0.660 0.630 3 0.590 0.605 0.600 0.590 4 0.745 0.740 0.735 0.745 5 0.695 0.695 0.680 0.695 6 0.640 0.635 0.635 0.630 7 0.655 0.665 0.650 0.650 8 0.640 0.645 0.620 0.610 9 0.670 0.675 0.670 0.665 10 0.655 0.660 0.645 0.650 Table 14.10: Access times (ms) for disk drives.
Brand Computer 1 2 3 4 5 A 35 42 31 30 —
B 41 45 — 32 40 C — 40 42 33 39 D 32 — 33 35 36 E 40 38 35 — 37 Table 14.11: Tensile strength of uniform twill.
Fabric Machines strips m1 m2 m3 m4 s1 18 7 5 9 s2 9 11 12 3 s3 7 11 11 1 s4 6 4 10 8 s5 10 8 6 10 s6 7 12 3 15 s7 13 5 15 16 s8 1 11 8 12 drives. The data are given in Table 14.10. Analyze the data using an additive two-factor model.
Focus your analysis on identifying differences among brands.