.

The data shown here are concentration.

readings from a chemical process, made every 30 minutes (read down, then across from left to right).

(a) Calculate the sample aurocorrela-
tion function and provide an inter-
pretation.

(b) Construct an individuals control chart with the standard deviation estimated using the moving range method. Provide an interpretation of this control chart,

(c) Fit a first-order. autoregressive model x, = € + px ,- 1 + 8, to the data.
Set up an individuals control chart on the residuals from this model.
. Interpret this chart.

(d) Are the residuals from the model in pant

(c) uncorrelated? Does this have any impact on your interpreta-
tion of the control chart from part (c)?

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