2. A case study deals with semiconductor wafer diameter.

11 The data set, consisting of samples of size 2 that are taken from 20 lots, can be found in SqcSemicondDiam.txt.

(a) Use commands similar to those given in Example 13.3-1 to construct an S and an R chart. Comment on what these charts suggest about the process variability.

(b) Use commands similar to those given in Example 13.2-2 to construct a 3σ X chart, using the estimator

!σ2 given in (13.2.5). What does the chart suggest regarding the process mean?

(c) Repeat part

(b) using the estimator !σ1 given in

(13.2.5). Has the conclusion from part

(a) changed?