(i) In statistical quality control, which would be the more sensitive control limits, ± 3s or ± 2s?
(ii) A manufacturer likes to prepare a statistical quality control chart for the number of mounting bracket hole discrepencies in the power supply chassis of a TV set. Twenty samples of size 200 have been taken and discrepancies are as follows?
|
Sample number
|
Number of discrepencies
|
Sample number
|
Number of discrepencies
|
|
1
2
3
4
5
6
7
8
9
10
|
11
7
4
1
5
13
6
5
3
0
|
11
12
13
14
15
16
17
18
19
20
|
5
7
9
5
17
18
9
5
7
0
|
Determine the preliminary control limits. Construct the control chart. Plot the twenty samples. Is the process under control? 5+15