How Acceptable Quality Level (AQL) Works

Quality control is one of the most critical aspects of manufacturing a product. No one wants to spend their hard-earned money on a low-quality product. The Acceptable Quality Level (AQL) is one of the concepts that deal with quality control. In more technical terms, AQL is the quality level that is the worst tolerable.

As different industries have different standards and specific sets of guiding principles, they have different standards for AQL. Some industries accept minor/micro defects, while others demand AQL be zero for the products to be accepted. An example of the latter is the medical and health industry: a minor fault in medical devices can give incorrect results or, worse, may put patients' lives in danger.

Products are selected at random from a batch to determine whether or not they meet AQL. The manufacturer tests the selected products for defects. If the number of defective products is below the AQL, the product is accepted; if the percentage of defects fails to meet the AQL standards, the manufacture rejects the tested products and possibly the batch.

Example of Acceptable Quality Level (AQL)

Let us assume that the acceptable quality level (AQL) for your company is equal to 5%, and the number of products in a batch is equal to one hundred. So, the minimum number of faults acceptable in the sample according to AQL is five. If the number of defective products in the sample is more than five, the manufacturer rejects the entire batch. If the number of faulty products is less than or equal to five, the batch will be accepted.

Manufacturers take extreme precautions in the manufacturing process to avoid their products getting rejected for not meeting the AQL standards.

Types of Acceptable Quality Level (AQL) Defects

Defects are factors that lead to malfunctioning of the products. Defects are classified differently depending on the standards of the industry in question.

1. Critical defects: These are the defects that, when accepted, can injure/harm the users of the products. The acceptable quality level is zero for these kinds of defects. An excellent example of this is in defense or police forces, where the products' functionality is highly critical to carry out their jobs. If defective products are accepted, there are high chances that they may harm or even kill the officers handling them.

2. Major defects: These are the defects that are usually not acceptable, as they will more probably lead to the failure of the whole product. The Acceptable Quality Level for major defects is 2.5%. A good example is the lock manufacturing industry. A defective locking mechanism makes a lock useless and makes it unusable.

3. Minor defects: The defects which are not likely to reduce the quality/usability of the product. The Acceptable Quality Level for minor defects is 4%. For example, you could consider color differences as minor defects. Light pink instead of dark pink will not impact the working or usability of the product.