The data set in DS 14.1.2 shows the results of an experiment performed to investigate how the deviation from specification of the width of a contact lens at its center point may depend on the type of material used to make the lens and the amount of magnification provided by the lens.
(a) Construct the analysis of variance table.
(b) Plot the residuals for each of the four types of material. Which material would you recommend be employed to minimize the variability in the deviations from specification?