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August 15th, 2017 
admin STATISTICAL PROCESS CONTROL
ONES CHEMICAL COMPANY
Ones Chemical Company customers have complained regarding the sulfate content of the
companys product. Every customer allows some sulfate content, but theoretically there
should be none. The usual customer specification is 90 parts per million (PPM) sulfate.
The quality control department at Ones feels that there is no problem with sulfate content,
which has been averaging just over 50 PPM. The production department estimates that a
substantial investment would be required to lower the amount of this contaminant. These
two departments, after consulting with the marketing department and customers, suggest
that a control chart be set up to monitor sulfate content. Five samples will be tested per day
and plotted as one point on the chart.
Use the data in Table 1 to set up the control limits. Then, after the limits are in place for this
process, use Table 2 to determine whether or not the process remains in control for the
week of April 610.
TABLE 1 Original Ones Chemical
Company data
Date
1
2
3
4
5
March 2
57
54
62
45
36
3
56
54
47
42
62
4
40
70
58
45
44
5
52
58
40
52
46
6
57
42
52
58
59
9
62
49
42
33
55
10
40
39
49
59
48
11
64
50
42
57
50
12
58
53
52
48
50
13
60
50
41
41
50
16
52
47
48
58
40
17
55
40
56
49
45
18
47
48
50
50
48
19
50
50
49
51
51
20
51
50
51
51
62
23
51
50
49
50
50
24
45
47
70
46
36
25
35
48
39
47
26
55
70
50
30
51
27
49
38
64
36
47
30
59
62
40
54
64
31
36
33
49
48
56
1
50
67
53
43
40
2
44
52
46
47
44
3
April
50
70
45
50
47
41
TABLE 2 Data for week of April 6
10
Date
1
2
3
4
5
April 6
63
49
50
45
53
7
57
70
45
52
61
8
45
38
46
54
52
9
48
52
39
57
61
10
45
53
48
46
66
DISCUSSION QUESTION
Does the process remain in control? Does the data for March appear to be in control? Please
support your with calculations.
1. Set up three-sigma control limits with the given data.
2. Is the process in control? Why?
3. Based on your analysis, is there a quality problem? If so, which one?
4. What advice would you give the company based on the information that you have?
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