South of the Borders, Inc. is a custom wallpapers and borders manufacturer. While their products vary in visual design, the manufacturing process for each of the products is similar. Each day a sample of 100 rolls of wallpaper border is sampled and the number of defective rolls in the sample is noted. The number of defective rolls in samples from 25 consecutive production days follows. The quality engineer is trying to establish the control limits for fractional nonconforming.
(a) Using the data, compute the centerline and control limits for the p chart.
Day n Defective Rolls
1 100 13
2 100 4
3 100 7
4 100 11
5 100 8
6 100 10
7 100 2
8 100 9
9 100 12
10 100 6
11 100 4
12 100 7
13 100 9
14 100 8
15 100 9
16 100 3
17 100 5
18 100 14
19 100 10
20 100 11
21 100 6
22 100 6
23 100 9
24 100 3
25 100 10