Question

Question 3:

In “Orthogonal Design for Process Optimization and Its Application to Plasma Etching”, an experiment is described to determine the effect of flow rate on the uniformity of the etch on a silicon wafer used in integrated circuit manufacturing. Three flow rates are used in the experiment, and the resulting uniformity (in percent) for six replicates is shown below.

Flow	Observations
125	2.7	4.6	2.6	3.0	3.2	3.8
160	4.9	4.6	5.0	4.2	3.6	4.2
200	4.6	3.4	2.9	3.5	4.1	5.1

1. Does flow rate affect etch uniformity? Use α = 0.05.
2. Do the residuals indicate any problems with the underlying assumptions?
3. Use the Kruskal-Wallis procedure with α = 0.05 to test for differences between mean uniformity at the three different flow rates.

Answer 1