There are two methods can be used to examine products' quality: whole inspection and sampling inspection
n Whole Inspection means taking examining on each product, jetting out unqualified one so the others are all qualified. However, this method is applicable when the quantity of product is not very large. So the sampling inspection is more common.
n We use the internationally standard tables, which called ANSI Z1.4-2003, to take sampling inspection (As shown below). The sampling has three levels: Level III, Level II and Level I. We usually use Level II to take sampling inspection. In addition, we use 0.010, 1.0, 1.5, 2,5, 4.0,6.5 as defect level(AQL). The defects can be divided into critical defect, major defect and minor defect.
n E.G.: we do inspection for 4000pcs electrical products. The sampling level is level II and the defect level(AQL) is 0.010, 1.5, 2.5. In this condition, we will randomly select 200pcs products in 4000pcs to take inspect. The critical detects will be 0, Major defects will be 7, and Minor defects will be 10