Capability of the film thickness process. The specifications call for film thickness 830 ± 25 mm × 10-4.
(a) What is the estimate σ^ of the process standard deviation based on the sample standard deviations (after removing Samples 1 and 10)? Estimate the capability ratio Cp and comment on what it says about this process.
(b) Because the process mean can easily be adjusted, Cp is more informative than Cpk. Explain why this is true.
(c) The estimate of Cp from part (a) is probably too optimistic as a description of the film produced. Explain why.