100-Metodos-de-Qualidade-Total

DATA COLLECTION, ANALYSIS AND DISPLAY 195
Example
A company is monitoring the number of defective bindings of a report. A
binding is defective when the contents overlap the outer covers. A sample
of 100 reports is taken on a daily basis and the figures are as follows:
Lot no.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Total
Defective lapping
(np)
5
6
5
4
2
1
2
o
2
3
4
3
4
3
2
3
2
4
3
2
60
Sample size = 100
'i.np = 60
np = 60/20 = 3
P = 3/100 = 0.03
3vnp = 5.20
V1 -p = 0.985
3vnp x V1 -p = 5.12
UCL = 3 + 5.12 = 8.12
LCL = 3- 5.12 = 0
The control chart shows that the process is under statistical control (Figure 1
on page 196).
Reference
Mal Owen (1989b) SPC and Continuous Improvement. London: IFS Publications.