The viscosity of a chemical product is read every two
The viscosity of a chemical product is read every two minutes. Some data from this process are shown in Table 10E.11 (read down, the across from left to right).
(a) Is there a serious problem with autocorrelation in these data?
(b) Set up a control chart for individuals with a moving range used to estimate process variability. What conclusion can you draw from this chart?
(c) Design a CUSUM control scheme for this process, assuming that the observations are uncorrelated. How does the CUSUM perform?
(d) Set up an EWMA control chart with = 0.15 for the process. How does this chart perform?
(e) Set up a moving center line EWMA scheme for these data.
(f) Suppose that a reasonable model for the viscosity data is an AR(2) model. How could this model be used to assist in the development of a statistical process-control procedure for viscosity? Set up an appropriate control chart, and use it to assess the current state of statistical control.
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