What is AQL?


Sampling protocols can vary, but one such method is called Acceptable Quality Limit, or AQL.

When a manufactured product is delivered, you want to have full confidence that the units are up to par. However, checking every unit is often not feasible, especially with high-quantity orders. Instead, a number of samples can be selected for inspection to provide insight into the quality of the entire order. Sampling protocols can vary, but one such method is called Acceptable Quality Limit, or AQL.

How AQL works

Sampling is a statistical process that utilizes qualifiers to determine if a large batch of a product falls within defined tolerances. To properly sample a product, there must be acceptable quality limits. These are numerical values assigned to act as a threshold for acceptability. These limits are used in conjunction with the level of inspection that is desired, based on a specific product and its requirements. The overall number of products in an order and sample sizes for items to be inspected will also be needed.

AQL also considers the types of defects to ensure they’re weighted properly in the determination. These are typically rated as minor defects, major defects, and critical defects. This system makes issues easier to qualify and categorize to accurately reflect the problem. 

Setting up an AQL sampling plan

AQL sampling plans can be tailored to several specific uses, such as production monitoring, product inspections, and safety inspections. The first step in creating a plan is to identify which scenario best reflects your needs. A professional can help you figure this out.

Then, an AQL must be determined. This is a number that correlates with an acceptable percentage of defects and can vary with different products. For example, medical devices will have lower limits than non-essential items. After the limits are established, a variety of factors to use in the evaluation will be determined. These variables may include batch size, level of inspection, and sampling level.

Once this work is complete, you’ll want to establish your sample size and outline acceptability. Sample size is the amount of product that will be taken and inspected at random per order. Then, criteria need to be developed to outline how many of the sampled products need to be rejected for the batch to fail the inspection.

When executing the plan, you’ll want to randomly select the number of samples to get a more statistically accurate representation of the lot. Each part will be inspected against the criteria outlined in the plan. In combination, the plan and inspections can inform whether the product order should be accepted. If the entire process of developing a plan sounds complicated, it’s because a well-developed strategy takes time and professional experience to execute properly.

Working with Factored Quality

If you’re looking to perform AQL sampling for your products, reach out to Factored Quality. We have the infrastructure and expertise to book professionals who can help you select, develop, and execute the right AQL sampling plan for your specific situation. Factored Quality worries about quality control so you don’t have to. Find out what we’re all about and how we can meet your needs.

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