Statistical Process Control Transition Rules for Skip Lot Qualification
Transitioning to skip-lot sampling demands a proven Cpk of 1.33 across consecutive lots and contract rules that force instant reversion to full inspection upon any defect.
Skip-Lot Qualification
Meaning
Audit reduction protocols allow a purchaser to inspect only a fraction of the total batches received from a supplier with a proven history of high quality. Achieving skip-lot qualification reduces the administrative burden and testing costs for both parties in a supply chain. The procedure follows the rules set out in the GB/T 13263 standard, which defines how to transition from every-lot inspection to a skip-lot state.
Performance Eligibility
Criteria for entering this reduced inspection mode typically include a long period of zero defects and a stable manufacturing process. A supplier must demonstrate that their internal quality controls are effective enough to maintain standards without constant external verification. Documentation of the last ten or twenty batches often serves as the evidence for this status.
Sampling Reduction
Inspections occur at a predetermined frequency, such as every fourth or fifth lot, once the qualification is granted. This allows the buyer to focus their laboratory resources on new or high-risk vendors while maintaining a basic level of oversight on trusted partners. The specific skip frequency is a matter of contractual agreement and statistical risk assessment.
Reinstatement Trigger
Failure of a single lot during the skipping phase causes an immediate return to normal inspection. This safeguard ensures that any degradation in quality is detected before it affects a large volume of goods.