A process was set to produce rivets of 10 mm length. The first 32 pieces made by the process were found to have the following lengths (in mm) :
|
|
9.9
|
10.0
|
10.0
|
9.9
|
9.9
|
9.9
|
10.0
|
10.0
|
10.1
|
10.1
|
|
10.0
|
10.0
|
9.9
|
10.1
|
10.1
|
9.9
|
9.9
|
10.1
|
10.0
|
10.1
|
10.0
|
|
9.9
|
9.9
|
9.9
|
10.1
|
10.0
|
10.0
|
10.1
|
10.0
|
10.0
|
10.0
|
|
i. Plot $\overline{X}$ and R control chart for the process, taking data for A2, D3 and D4 from the following table.
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No. of observations in the sample
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2
|
3
|
4
|
5
|
6
|
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A2
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1.88
|
1.023
|
0.729
|
0.577
|
0.483
|
|
D3
|
0
|
0
|
0
|
0
|
0
|
|
D4
|
3.276
|
2.575
|
2.282
|
2.115
|
2.004
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ii. If the process is not under statistical control, discuss what steps should be taken to make the control chart viable?