In addition to setting the AQL, the buyer should choose the sampling plan from the different inspection levels, here we break down the main sampling options for quality control inspection to help guide you determine scope of inspection that is best for you and your product.
Using statistical sampling based on acceptable quality limits (AQL), acceptance sampling decides the sample sizes for different order quantities, and these different sample sizes are the origin of GI, GII, and GIII.
General Inspection Levels
These main inspection levels – “GI”, “GII” and “GIII” – stand for general inspection level 1, 2 and 3, respectively. These three different levels indicate sample sizes of one lot size for a non-destructive inspection. The sample size of general inspection levels is applied by the inspector to the workmanship of the products during visual inspection. Any defects found in terms of workmanship are taken into account in the AQL result of the inspection. Any professional AQL chart will show the GI, GII, and GIII sample size of each group of lot sizes.
Reduced inspection (or level-I inspection):
Has this supplier passed most previous inspections? Do you feel confident in their products quality? Instead of doing no quality control, buyers can check less samples by opting for a level-I inspection.
However, settling on this level by default, less samples are inspected. This inspection level is appropriate when the client is confident that the quality of the products is acceptable.
Normal inspection (or level-II inspection):
It is the most widely used inspection level, to be used by default.
Tightened inspection (or level-III inspection):
If a supplier recently had quality problems, this level is appropriate. more samples are checked. This inspection level is used for suppliers that recently had severe quality problems, or for high-value products. It can also be interesting for small quantities, where the inspection would take only one day whatever the level chosen.
Example to get an clearer understanding
|Lot Size||General Inspection I
|General Inspection II
|General Inspection III
However, the lot size is not the only factor at work when determining the sample size. There are many other elements that need to be taken into account, we can discuss these elements later.