Question: Workers at a packaging operation shovels a granular product from a large pile into sacks that are then sealed and placed on pallets for shipping. A sequence of 25 subgroups each consisting of the weights of 5 sacks has been recorded as follows:
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Observations
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Subgroup #
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Sack 1
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Sack 2
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Sack 3
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Sack 4
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Sack 5
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1
|
35.4
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35.6
|
34.8
|
34.7
|
34.8
|
|
2
|
36
|
35.6
|
34.9
|
34.8
|
35.9
|
|
3
|
35.2
|
35
|
35
|
35.4
|
35.1
|
|
4
|
34.8
|
35.8
|
35.2
|
35
|
34.9
|
|
5
|
34.2
|
35
|
36.1
|
34.9
|
35.1
|
|
6
|
36
|
35
|
35.2
|
34.8
|
34.9
|
|
7
|
36.1
|
34.9
|
34.5
|
35
|
35.1
|
|
8
|
35.1
|
35
|
35.6
|
34.9
|
36.2
|
|
9
|
35
|
35.6
|
36.1
|
34.8
|
35.6
|
|
10
|
35.4
|
35.8
|
36
|
34.2
|
36
|
|
11
|
35.2
|
35.3
|
35.2
|
35.9
|
34.8
|
|
12
|
35.9
|
36
|
35.1
|
35.1
|
35.6
|
|
13
|
35.2
|
35.6
|
35
|
34.9
|
35
|
|
14
|
35.2
|
35.6
|
35.8
|
35
|
35.1
|
|
15
|
34.9
|
34.8
|
35
|
35.2
|
34.9
|
|
16
|
35.2
|
35.3
|
35.2
|
35.6
|
35.1
|
|
17
|
35.6
|
35.8
|
35.2
|
35.4
|
34.9
|
|
18
|
35.2
|
35.6
|
35.4
|
35.6
|
35.2
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|
19
|
34.7
|
34.9
|
35.6
|
35.2
|
35
|
|
20
|
35
|
35.1
|
35.6
|
35
|
35.1
|
|
21
|
35.6
|
35
|
35.8
|
35.2
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34.6
|
|
22
|
34.9
|
35.1
|
35.6
|
35
|
35.2
|
|
23
|
35.9
|
36
|
35.2
|
36
|
35.2
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|
24
|
35.2
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35.1
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35.4
|
34.9
|
35.1
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|
25
|
35.2
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35.2
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35.1
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35.6
|
34.9
|
a- What is the appropriate control chart that can be used by the quality engineer in this case?
b- Determine the control limits (show your calculations)
c- Construct the appropriate control chart for the data above using MINITAB.
d- Is the process in-control? If not, when does the out-of-control behavior occur?
e- If the process is found to be out of control, drop the out-of-control points and use MINITAB to re-construct the control chart.
f- Is the process now in-control? If not, what to do next?