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.
Acceptance Sampling
Meaning
Statistical method for determining whether a batch of material meets specified quality levels. Manufacturing contracts in China frequently use acceptance sampling to define the point of risk transfer between a supplier and a buyer. This procedure involves selecting a random sample from a lot and comparing the number of defects found against a predetermined threshold.
If the count of non-conforming units exceeds the limit, the entire shipment is rejected. The GB/T 2828.1 standard provides the primary administrative framework for these inspections within the Chinese domestic market.
Contractual Governance
Legal standing of a batch depends on the inspection parameters defined in the purchase agreement. While acceptance sampling offers a mathematical basis for rejection, the People’s Republic of China Contract Law requires that such methods are explicitly cited to be enforceable during a dispute. Parties specify the acceptable quality level and the inspection level to balance the risk of producer and consumer errors.
Regulatory Alignment
National standards issued by the State Administration for Market Regulation govern how sampling plans are constructed for different product categories. These standards provide a repeatable logic that courts can verify. Under the Product Quality Law, a manufacturer remains liable for latent defects even if a lot passes a sampling check.
A formal record of the sampling process provides evidence that the buyer performed due diligence.
Operational Limit
Execution of these tests occurs before the buyer signs the delivery receipt. Once the acceptance sampling confirms compliance, the burden of proof for subsequent damage shifts to the logistics provider. High-value components often require tighter thresholds than general commodities.
This limit prevents suppliers from shipping marginal batches that could disrupt downstream production lines.