. Consider a T control chart for moni- toring p=6 quality characteristics. Suppose that the subgroup size...

.

Consider a Tª control chart for moni-

toring p=6 quality characteristics.

Suppose that the subgroup size is n = 3 and there are 30 preliminary samples available to estimate the sample covari-

ance matrix.

(a) Find the phase II control limits assuming that cx = 0.005.

(b) Compare the control limits from part

(a) to the chi-square control limit. What is the magnitude of the difference in the two control limits?

(c) How many preliminary samples would have to be taken to ensure that the exact phase II control limit

" Is within 1% of the chi-square con-

trol limit?