. Consider the p = 9 process variables in Table 10-5.

(a) Perform a PCA on the first 30 obser-

vations. Be sure to work with the standardized variables.

(b) How much variability is explained if only the first r = 3 principal compo-

nents are retained?

(c) Construct an appropriate set of pair-

wise plots of the first r = 3 principal component scores.

(d) Now consider the last 10 observa-

tions. Obtain the principal compo-

nent scores and plot them on the chart in part (c). Does the process seem to be in control?