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 (l = 2) at each combination of levels of the factors, yielding a total of 54 observations on output. the sums of squares were ssa = 14,144.44, ssb = 5501.27, ssc = 244,896.39, ssab = 1049.62, ssac = 62.67, ssbc = 331.67, sse = 3126.5, and sst = 270,024.33.