
Chapter 17
PB
Statistical Quality Control
727
Cloth lot number Number of defects
12 4
13 3
14 0
15 0
16 4
17 5
18 6
19 3
20 4
21 2
22 3
23 1
24 6
25 5
Solution: Centreline, upper control limit (UCL), and lower control limit (LCL) can be determined
as below:
Centreline (CL) = c =
=
4 546 5
4.2
Upper control limit (UCL) = cc+=+× =3423 10 3482
2.04939
Lower control limit (LCL) = cc−=−× =−3423 1 9481
2.04939
Practically, the lower control limit cannot be negative; hence, the lower control limit is taken as
zero. The c chart shown in Figure 17.15 clearly exhibits that all the points are within the control
limits. Hence, it can be said that the process ...