A scientist collects experimental data on the radius of a propellant grain, y, as a function of powder temperature, extrusion rate, and die temperature. Results of the three-factor experiment are as follows: Powder Temp 150 190 Die Temp Die Temp Rate 220 250 220 250 12 82 124 88 129 24 114 157 121 164 Resources are not available to make repeated experimental trials at the eight combinations of factors. Itis believed that extrusion rate does not interact with die temperature and that the three-factor interaction should be negligible. Thus, these two interactions may be pooled to produce a 2 d. f. error term. (a) Do an analysis of variance that includes the three main eects and two two-factor interactions. Determine what eects inuence the radius of the propellant grain.
(b) Construct interaction plots for the powder temperature by die temperature and powder temperature by extrusion rate interactions.
(c) Comment on the consistency in the appearance of the interaction plots and the tests on the two interactions in the ANOVA.