In the apparel business, before accepting the finished garments from an apparel manufacturer buyer does an inspection of the garments. As the whole lot of goods inspection is not viable, also not advisable, inspection is done on a sampling basis. In product quality inspection how much percentage of defective pieces will be accepted depends on the acceptable quality level. AQL is the short name of acceptable quality level.
In the following table, a sampling plan is given for final shipment inspection. The AQL level varies from process to process, product to product, and even buyer to buyer.
Definition of AQL
The AQL (Acceptable Quality Level) is the maximum percent defective that for the purpose of sampling inspection can be considered satisfactory as a process average.Table: Sampling plan for shipment inspection:
Lot or Batch size
|
Sample size Code Letter
|
Sample Size
|
Acceptable Quality Level
|
|||||
2.5
|
4.0
|
6.5
|
||||||
Ac
|
Re
|
Ac
|
Re
|
Ac
|
Re
|
|||
2 – 8
|
A
|
2
|
0
|
1
|
0
|
1
|
0
|
1
|
9 – 15
|
B
|
3
|
0
|
1
|
0
|
1
|
0
|
1
|
15 – 25
|
C
|
5
|
0
|
1
|
0
|
1
|
0
|
1
|
26 – 50
|
D
|
8
|
0
|
1
|
1
|
2
|
1
|
2
|
51-90
|
E
|
13
|
1
|
2
|
1
|
2
|
2
|
3
|
91-150
|
F
|
20
|
1
|
2
|
2
|
3
|
3
|
4
|
151-280
|
G
|
32
|
2
|
3
|
3
|
4
|
5
|
6
|
251-500
|
H
|
50
|
3
|
4
|
5
|
6
|
7
|
8
|
501-1200
|
J
|
80
|
5
|
6
|
7
|
8
|
10
|
11
|
1201-3200
|
K
|
125
|
7
|
8
|
10
|
11
|
14
|
15
|
3201-10000
|
L
|
200
|
10
|
11
|
14
|
15
|
21
|
22
|
10001-35000
|
M
|
315
|
14
|
15
|
21
|
22
|
21
|
22
|
Source: ANSI/ASQ Z 1.4 The Sampling procedures and table for inspection by attributes
|
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Check the AQL chart for quality application.
How to Read AQL Table?
Lot or Batch size:This means the total number of pieces the inspector is going to check or inspect. (i.e. if you have been offered a shipment of 600 pieces order quantity, the batch size of this shipment will fall under 501 to 1200 pieces (Code-J)
Sample size Code letter:
Sample size Code letter:
This code is indicative of a range of batch sizes. (Code 'G' means your lot size range is from 151 pieces to 280 pieces.
Sample size:
Sample size:
It means how many pieces will be picked up for shipment inspection from the total offered pieces (Batch).
Ac (Accepted):
Ac (Accepted):
The number in this column denotes that if the inspector finds up to that many defective pieces the shipment will be accepted by the buyer.
Re (Rejected):
Re (Rejected):
On the other hand, the number in this column denotes that if the inspector finds defective pieces or more than the listed number, the shipment will be rejected (or ask the manufacturer for 100% inspection and re-offer for final inspection) by the buyer.
Example:
Suppose you have been offered a shipment of 1000 pieces for inspection.
Select the range from the table, it is 501-1200.
Now from the AQL table, you need to select the number of samples you are going to actually inspect. According to the above AQL chart, you need to select 80 pieces out of 1000 pieces.
Now assume that you are inspecting at 2.5 AQL.
So, after inspecting all 80 pieces if you found 5 or less than 5 defective pieces, you need to accept the shipment. And if you find 6 or more than 6 defective pieces in 80 samples, you need to reject that shipment.
Example:
Suppose you have been offered a shipment of 1000 pieces for inspection.
Select the range from the table, it is 501-1200.
Now from the AQL table, you need to select the number of samples you are going to actually inspect. According to the above AQL chart, you need to select 80 pieces out of 1000 pieces.
Now assume that you are inspecting at 2.5 AQL.
So, after inspecting all 80 pieces if you found 5 or less than 5 defective pieces, you need to accept the shipment. And if you find 6 or more than 6 defective pieces in 80 samples, you need to reject that shipment.