Question

Problem 4. A high-voltage power supply should have a nominal output voltage of 350 V. A sample of four units is selected each day and tested for process-control purposes. The data (see sheet Problem4 in Homework 4.xlsx) give the difference between the observed reading on each unit and the nominal voltage times ten; that is, ?? = (observed voltage on unit ? - 350)*10 (a) Set up ?̅ and ? charts on this process. Is the process in statistical control? (2 points) (b) If specifications are at 350 V ±5 V, estimate ? and ? , ? and ? ? (2 points) ? ??? ?? (c) What can you say about process capability ??? (2 points)

Sample	x1	x2	x3	x4	Xbar	R
1	6	9	10	15	10	9
2	10	4	6	11	7.75	5
3	7	8	10	5	7.5	5
4	8	9	6	13	9	7
5	9	10	7	13	9.75	6
6	12	11	10	10	10.75	2
7	16	10	8	9	10.75	7
8	7	5	10	4	6.5	6
9	9	7	8	12	9	4
10	15	16	10	13	13.5	6
11	8	12	14	16	12.5	8
12	6	13	9	11	9.75	7
13	16	9	13	15	13.25	7
14	7	13	10	12	10.5	6
15	11	7	10	16	11	9
16	15	10	11	14	12.5	5
17	9	8	12	10	9.75	3
18	15	7	10	11	10.75	8
19	8	6	9	12	8.75	6
20	13	14	11	15	13.25	4

Answer 1

Yes, The Process is in Statistical Control.

Sample size	4
	Number of samples	20
		Mean	Range
	Upper Control Limit, UCL	14.88	14.26
	Center	10.33	6.25
	Lower Control Limit, LCL	5.77	0.00

C-hat_p = 5.49, so the process is capable.