What Is Acceptable Quality Level (AQL)?

The acceptable quality level or limit (AQL) is a crucial measure in quality control. It applies to products and is defined in ISO 2859-1 as the maximum number of defective items that can be considered acceptable during random sampling inspections of a production batch.

Defined in ISO 2859-1 as the "worst tolerable" quality level, AQL helps manufacturers and buyers agree on acceptable defect levels for products. AQL is typically expressed as a percentage or ratio, reflecting the number of defects compared to the total quantity produced. For example, if a production run of 5,000 units has an AQL of 1%, no more than 50 defective items (1% of 5,000) would be acceptable for the batch. Any amount over 50 defective items would lead to a rejection.

AQL standards vary by industry, with stricter levels applied to products where defects could pose significant risks, such as in the medical field, where even a single defect can pose serious health risks, leading to stringent regulatory requirements and a near zero-defect tolerance.

How Acceptable Quality Level (AQL) Works

AQL is an international standard used to determine the quality of products by inspecting a sample from each batch. It sets the maximum number of defective units that are allowed before the entire batch is rejected.

Goods in a sample are tested randomly, and if the number of defective items is below the predetermined amount, that product is said to meet the AQL. If the AQL isn't reached for a particular sampling of goods, manufacturers will review the various parameters in the production process to determine the areas causing the defects.

For example, consider an AQL of 1% on a production run. This percentage means no more than 1% of the batch can be defective. If a production run comprises 1,000 products, only 10 (1%) of the products can be defective. If 11 products🌠 are defective, the entire batch is scrapped. This figure of 11 or more defective products is the rejectable quality level (RQL).

The AQL is an important statistic for companies seeking a Six Sigma level of 澳洲幸运5官方开奖结果体彩网:quality control, a methodology developed in 1986 by Motorola, Inc. It aims to minimize defects and reduce variability to achieve near-perfect quality levels.

Industry Differences in AQL Standards

The AQL of a product can vary from 澳洲幸运5官方开奖结果体彩网:industry to industry. For example, medical products are more likely to have more stringen🔯t AQL because defective products can result in health risks.

In contrast, a product with benign side effects from a possible defect may have a less strict AQL, such as the remote control for a TV. Companies have to weigh the added cost associated with stringent testing and potentially higher spoilage due to a lower defect acceptance with the 澳洲幸运5官方开奖结果体彩网:potential cost of a 澳洲幸运5官方开奖结果体彩网:product recall.

Customers would, of course, prefer zero-defect products or services—the ideal acceptable quality level. However, sellers and customers usually try to 澳洲幸运5官方开奖结果体彩网:🌳arrive at and set acceptable quality limits based on factors typically related ꧟to business, financial, and safety concerns.

Using AQL Tables

AQL tables (also called AQL charts) are designed to allow users to reference a standard for what qualifies as an acceptable number of defects in manufactu💫ring. These tables, which are part of ISO 2859, help users identify ✨how many defects are permissible to meet a specific AQL standard.

For example, let's say a company orders 30,000 hats from a clothing manufacturer that will be produced in one batch, and the buyer and producer have agreed on AQL 0.0 for critical defects, AQL 3.0 for major defects, and AQL 5.0 for minor defects. The AQL tables would guide them in determining how many hats need to be inspected to ensure compliance with these standards during production.

AQL Defects

Instances of failure to meet customer quality requirements are termed as defects, which fall int🦋o three categor🍃ies:

1. Critical defects: These are defects that could harm users and are entirely unacceptable, with an AQL set at 0%.
2. Major defects: Defects usually not acceptable by the end-users, as they'll likely result in failure. The AQL for major defects is typically set at 2.5%.
3. Minor defects: These defects do not significantly impact the product's usability but deviate from specified standards. Some end-users might still accept these products, with an AQL usually set at 4%.

AQL in Practice

Acceptable quality level (AQL): AQL is typically considered the worst quality level still considered satisfactory. It's the maximum percent defective that can be considered satisfactory. The probability of accepting an AQL lot should be high. A probability of 0.95 translates to a risk of 0.05. This means there's a 95% chance of accepting the lot, with a 5% risk of rejecting it.

Rejectable quality level (RQL): This is considered unsatisfactory and sometimes known as lot tolerance percent defective (LTPD). Some tables have standardized the consumer’s risk as 0.1. meaning there's a 10% chance that a lot with defects at the RQL level will be mistakenly accepted. The probability of accepting an RQL lot is low.

Indifference quality level (IQL): This quality level is between AQL and RQL. Different companies maintain different interpretations of each defect type. However, buyers and sellers agree on an AQL standard that's appropriate to the level of risk each party assumes. These standards are used as a reference during a pre-shipment inspection.

The Bottom Line

AQL can be a useful figure to help ensure that large orders for manufacturing are completed to a level of standard that a buyer demands. It also all🅰ows the seller to be efficient in their production while maintaining the standard set by the buyer. It is generally used in large-scale orders of production, and is helpful in keeping both buyer and seller happy while producing good quality products.