Table 19.14 presents some details on the
mean and range of 11 samples drawn from a process during routine sampling and
inspection. The readings are the weight of a certain metal deposited on the
surface of a component used in an electro-mechanical device. The lower and
upper specification limits for the weight of metal to be deposited are 10.7 g
and 13.3 g, respectively. The
standard deviation for the process is found
to be 1.28. Assume the sample size to be four.
(a) Develop relevant control charts for the
process (Hint: Since the standard deviation of the population is known, the
control limits can be directly established, see endnote 3 for details)).
(b) Is the process under control? If not,
explain why and suggest what could be done.
(c) Compute the potential and actual
capabilities for the process. What do you infer from this computation? Do you
have any recommendations to make to the organization?