Problem 2

Best Book Stand is a manufacturer of wooden bookstands. The production manager at Best Book Stand tracks the number of defective book stands out of each lot of 750 finished products every week. The following data for 15 weeks has been collected when the production process was known to be in control.

Week	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
# of defectives per lot	5	8	12	3	18	21	6	9	7	11	3	11	12	8	10

In order to continuously check if the process is still under control, the manager continued collecting data for ten more weeks. Again, data indicates the number of defective book stands per lot of 750 for each week.

Week	16	17	18	19	20	21	22	23	24	25
# of defectives per lot	9	17	12	11	13	16	12	10	15	12

1. Calculate the 3 upper and lower control limits and the center lines for the proportion of defective book stands using data from when the process was known to be in control. (6 points)

Week	# defectives per lot	p
1	5	0.007
2	8	0.011
3	12	0.016
4	3	0.004
5	18	0.024
6	21	0.028
7	6	0.008
8	9	0.012
9	7	0.009
10	11	0.015
11	3	0.004
12	11	0.015
13	12	0.016
14	8	0.011
15	10	0.013

1. Construct the appropriate control chart(s) showing all 25 samples.

1. Is the process still in control? Why or why not?