An experiment has been run in a process that applies a coating material to a wafer. Each
An experiment has been run in a process that applies a coating material to a wafer. Each run in the experiment produced a wafer, and the coating thickness was measured several times at different locations on the wafer. Then the mean y1 and standard deviation y2 of the thickness measurement was obtained. The data [adapted from Box and Draper (1987)] are shown in the table below:
(a) What type of design did the experimenters use? Is this a good choice of design for fitting a quadratic model?
(b) Build models of both responses.
(c) Find a set of optimum conditions that result in the mean as large as possible with the standard deviation less than 60.
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