You are concerned about the quality of parts that you are receiving from your sup- plier. Consequently, you decide to take 25 batches of samples (where each sample consists of 50 units) and to do 100% inspection on these samples. The results are summarized below.
|
Batch number
|
Defectives
|
Sample size (n550)
|
|
1
|
5
|
50
|
|
2
|
6
|
50
|
|
3
|
5
|
50
|
|
4
|
6
|
50
|
|
5
|
3
|
50
|
|
6
|
3
|
50
|
|
7
|
6
|
50
|
|
8
|
5
|
50
|
|
9
|
3
|
50
|
|
10
|
5
|
50
|
|
11
|
5
|
50
|
|
12
|
7
|
50
|
|
13
|
8
|
50
|
|
14
|
10
|
50
|
|
15
|
10
|
50
|
|
16
|
6
|
50
|
|
17
|
5
|
50
|
|
18
|
4
|
50
|
|
19
|
5
|
50
|
|
20
|
5
|
50
|
|
21
|
6
|
50
|
|
22
|
5
|
50
|
|
23
|
6
|
50
|
|
24
|
3
|
50
|
|
25
|
4
|
50
|
|
Totals
|
136
|
1250
|
This forms the basis for your further analysis. Next, you collect information about 20 recent orders that you have received from your supplier in the last month. By the way, it is important to note that your supplier is aware that your firm is concerned about the quality of its parts. These are summarized below:
|
Sample Data - June
|
|
Sample Number
|
Sample size
|
Number of Defects
|
|
1
|
50
|
3
|
|
2
|
50
|
2
|
|
3
|
50
|
3
|
|
4
|
50
|
4
|
|
5
|
50
|
1
|
|
6
|
50
|
2
|
|
7
|
50
|
4
|
|
8
|
50
|
3
|
|
9
|
50
|
1
|
|
10
|
50
|
1
|
|
11
|
50
|
2
|
|
12
|
50
|
2
|
|
13
|
50
|
3
|
|
14
|
50
|
1
|
|
15
|
50
|
3
|
|
16
|
50
|
3
|
|
17
|
50
|
4
|
|
18
|
50
|
5
|
|
19
|
50
|
5
|
|
20
|
50
|
5
|
a. Given the information in this problem, calculate the p, UCL, and LCL from the baseline data. Use these parameters to construct an p control chart.
b. Plot the data from the June samples on the p chart derived in (a). What issues, if any, does this analysis reveal? What management actions would you recommend and why?
c. You receive a telephone call from your supplier informing you that they (the supplier) have significantly changed the production process for your orders at their facility. How would this affect the previous analysis (p control chart)?