problem:

\fAn article in the Journal of Coatings Technology (V 01. 60, 1988, pp. 27-32) describes a 24 factorial design used for studying a silver automobile basecoat. The response variable is distinctness of image (DOI). The variables used in the experiment are A = Percentage of polyester by weight of polyester/melamine (low value = 50%, high value = 70%) B = Percentage of cellulose acetate butyrate carboxylate (low value = 15%, high value = 30%) C = Percentage of aluminum stearate (low value = 1%, high value = 3%) D = Percentage of acid catalyst (low value = 0.25%, high value = 0.50%) The responses are (1) = 64.5, a = 78.4, b = 69.0, ab = 77.2, c = 73.2, ac = 77.0, kg: 77.6, (1056: 84.7, d = 60.1, ad = 65.7, M: 73.4, m = 73.2, cd = 68.7, 94: 75.7, W: 75.2, and W = 76.3. (a) Estimate the factor effects. (b) From a normal probability plot of the effects, identify a tentative model for the data from this experiment. (c) Using the apparently negligible factors as an estimate of error, test for signicance of the factors identified in part (b). Use u=0.05. (d) What model would you use to describe the process, based on this experiment? (e) Analyze the residuals from the model in part ((1) and comment on your ndings