Question

A manufacturing company makes runners for cabinet drawers. To assess the quality of the manufacturing process, the company collected one sample of 300 consecutively manufactured runners each day for 20 days and counted the number of defective items. The resulting sample data are:

Sample:             1      2      3      4      5      6      7      8      9    10
Sample Size:   300 300 300 300 300 300 300 300 300 300
Defectives:        8       6     11    15    12    11     9      6      5      4

The Upper Control Limit, UCL, for a p control chart based on the above data is

Answer 1

The Computations for Control Chart

Sample	Defectives d	p =d/300
1	8	0.026667
2	6	0.02
3	11	0.036667
4	15	0.05
5	12	0.04
6	11	0.036667
7	9	0.03
8	6	0.02
9	5	0.016667
10	4	0.013333
Total	87	0.29

In the usual noatations, we have

control limits for p chart are given by :