The output of a continuous extruding machine that coats steel pipe with plastic was studied as a function of the thermostat temperature profile (A, at three levels), the type of plastic (B, at three levels), and the speed of the rotating screw that forces the plastic through a tube-forming die (C, at three levels). There were two replications at each combination of levels of the factors, yielding a total of 54 observations on output. The sums of squares were

, and .

a. Construct the ANOVA table.

b. Use appropriate F tests to show that none of the F ratios for two- or three-factor interactions is significant at level .05.

SSE 5 3127.50 SST 5 270,024.33 SSAB 5 1069.62, SSAC 5 62.67, SSBC 5 331.67, SSA 5 14,144.44, SSB 5 5511.27, SSC 5 244,696.39,

(L 5 2)

c. Which main effects appear significant?

d. With , and , use Tukey’s procedure to identify significant differences among the levels of factor C.