The thickness of a metal part is an important quality parameter. Data on thickness (in inches) are given here, for 25 samples of five parts each.
(a) Using all the data, find trial control limits for and R charts, construct the chart, and plot the data. Is the process in statistical control?
(b) Use the trial control limits from part (a) to identify out-ofcontrol points. List the sample numbers of the out-of-control points. Continue eliminating points and revising control limits until the charts are based only on in-control observations