验货质量标准（AQL）

The quality inspectors in China use the MIL STD 105E tables, which are recognized standards by every industrial company.
This American standard now has equivalents in all national and international standardization organisations (ANSI/ASQC Z1.4, ISO 2859, NF06-022, BS 6001, DIN 40080).
This standard is a proven method to accept or reject a production lot by inspecting a randomly selected number of products.
This method is called ‘AQL’(acceptable quality level):

As a quality control company in China, QGS uses the Acceptable Quality Level (AQL) to establish a maximum allowable error rate or variation from the standard. Acceptance testing will cease immediately if the failure rate of the product being tested exceeds the minimum Acceptable Quality Level.
NB: It is important to note that Acceptance Sampling cannot provide 100% perfect products. The only way of achieving this is to produce 100% perfect products.

MIL STD 105E table:

Practically, QGS Quality Standards use the MIL STD 105E tables that are summarised below:

Table A :

Table B:

NB: What can I find out from the AQL tables?
Let's take a lot of 3,000 units to inspect, with an AQL of 2.5%.
According to Table B, the sample size is therefore 125 units, and the corresponding acceptance number is 7.

In other words:
     If the number of defective units is more than 7, the lot has to be rejected
     If the lot is accepted, it is commonly perceived that there is a maximum of 2.5% of defective units in the lot (with a failure risk percentage of less than 5%).