Guardos Medical Supply has been getting complaints from its major customer about
ID: 453469 • Letter: G
Question
Guardos Medical Supply has been getting complaints from its major customer about defective shipments. They gathered data for the past 8 weeks to track their defects, and this information is shown in the table below.
Type of Defect
Week
No. of shipments
No. of shipments with defects
Incorrect bill of lading
Missing products
Damaged product
Truck late
1
23
5
2
2
1
2
31
8
1
4
1
2
3
28
6
2
3
1
4
37
11
4
4
1
2
5
35
10
3
4
2
1
6
40
14
5
6
3
7
41
12
3
5
3
1
8
44
15
4
7
2
2
a. Use an appropriate quality tool (one of the 7 basic tools) that shows the relationship between the defect rate and time. Why is it better to use the defect rate instead of the number of defects?
b. Use an appropriate quality tool (one of the basic 7 tools) to show Vax where to focus their improvement efforts in order to reduce defective shipments.
Type of Defect
Week
No. of shipments
No. of shipments with defects
Incorrect bill of lading
Missing products
Damaged product
Truck late
1
23
5
2
2
1
2
31
8
1
4
1
2
3
28
6
2
3
1
4
37
11
4
4
1
2
5
35
10
3
4
2
1
6
40
14
5
6
3
7
41
12
3
5
3
1
8
44
15
4
7
2
2
Explanation / Answer
Type of Defect Defect rate Week No. of shipments No. of shipments with defects Incorrect bill of lading Missing products Damaged product Truck late No. of shipments with defects Incorrect bill of lading Missing products Damaged product Truck late 1 23 5 2 2 1 0.22 0.09 0.09 0.043 0 2 31 8 1 4 1 2 0.26 0.03 0.13 0.032 0.065 3 28 6 2 3 1 0.21 0.07 0.11 0.036 0 4 37 11 4 4 1 2 0.30 0.11 0.11 0.027 0.054 5 35 10 3 4 2 1 0.29 0.09 0.11 0.057 0.029 6 40 14 5 6 3 0.35 0.13 0.15 0.075 0 7 41 12 3 5 3 1 0.29 0.07 0.12 0.073 0.024 8 44 15 4 7 2 2 0.34 0.09 0.16 0.045 0.045 total 279 81 P bar (total Number of incorrect analysis/ total sample) 0.2903 Sp (sqrt (P bar*(1- p bar)/279) 0.0272 z (assumed at 95%) 1.96 UCL (p bar + z* Sp) 0.3436 LCL (p bar - z* Sp 0.2371 Control chart (one of the 7 basic tools of quality control) is an appropriate quality tool here , we can use p chart as it is good for showing relationship in defect rate and time. Using defect rate instead of number of defects is better because it is independent of number of samples. Therefore it brings an uniformity in the data. Focus should be on missing product in the shipment to improvement efforts in order to reduce defective shipments.
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