What is AQL?

AQL stands for Acceptable Quality Limit, and it is a statistical measurement used to determine whether the quality of a batch or lot of products meets the buyer's requirements. It helps to assess whether a production lot should be accepted or rejected based on a sample from the lot.

The Importance of AQL

The AQL standard helps manufacturers and suppliers assess the level of defects in a production lot and decide whether the lot meets the customer’s acceptable quality criteria. It provides a consistent and uniform method to determine the level of defects that is tolerable for the buyer and what would be considered unacceptable, leading to rejection.

How is AQL Calculated?

AQL is typically calculated based on a sample from a batch, with specific defect types classified as critical, major, or minor. Different AQL values are set for each category:

AQL Sample Calculation Process

The AQL value indicates the maximum number of defects allowed in a sample size. If the number of defects exceeds the set limits, the lot is rejected. The process involves:

• Sampling a certain number of units from the total lot.
• Assessing the defects found in the sample.
• Comparing the defect count to the AQL thresholds to decide whether to accept or reject the lot.

Key AQL Values

The AQL values can be selected based on the level of quality required by the buyer. The most common AQL values are:

• AQL 0.1%: Often used for critical items where defects could result in serious harm or danger.
• AQL 1.0%: Standard for high-end products where functionality is a priority.
• AQL 2.5%: Standard AQL for most general consumer goods, where a balance of quality and cost is necessary.
• AQL 4.0%: Tolerable for products where minor defects are acceptable.

Inspection Levels

The inspection level determines the sample size to be selected for inspection, with three standard levels:

• Level I (Reduced Inspection): Used for low-risk products, with smaller sample sizes.
• Level II (Normal Inspection): Most commonly used, where sample size is moderate and balanced.
• Level III (Special Inspection): For high-risk or high-value products, with larger sample sizes and stricter acceptance criteria.