A quality inspector took six samples, each with four observations (n=4), of the length of time for glue to dry. The analyst computed the mean of each sample and then computed the grand mean. All values are in minutes. Use this information to obtain three-sigma (i.e., z=3) control limits for means of future times. It is known from previous experience that the standard deviation of the process is .03 minute.
				SAMPLE
		1	2	3	4	5	6
	1	12.11	12.15	12.09	12.12	12.09	12.1
Observation	2	12.1	12.12	12.09	12.1	12.14	12.13
	3	12.11	12.1	12.11	12.08	12.13	12.09
	4	12.08	12.11	12.15	12.1	12.12	12.12
	Mean	12.1	12.12	12.11	12.1	12.12	12.11
b. (3p)
In this question, the standard deviation of the process is unknown. Refer to the data given in Q1-a. compute the uppor and lower limits for a mean control chart. To answer this question, you should refer Table 10.3 (p.433) in the textbook.
c. (3p)
Using the average range found in Q1-b, compute the control limits for a range chart. To answer this question, you should refer Table 10.3 (p.433) in the textbook.