AQL sampling

AQL stands for Acceptable Quality limit. It is a statistically sound way of taking samples.

Carrying out quality checks on [incoming] batches is often time-consuming. This often hinders the rapid flow of goods in your organization. Especially if more extensive checks are required. Still, as an organization you want to keep a grip on the quality of the goods that arrive. Poor quality of purchased goods can be disastrous for an organization.

Quality limit
With AQL you can take a sample and make an informed decision as to whether a supplied batch of goods can withstand the test of criticism. By taking a statistically sound sample of the batch, which is based on internationally recognized ISO standards. Based on the sample, you can use AQL tables to determine the acceptable quality limit of a batch.
The quality limit determines the maximum number of defects that may be found in a sample. If you have a higher rejection than the set limit, the entire batch must be rejected and, if necessary, fully inspected. The set limits also make it clear in advance what the boundaries are and no discussion is possible.

AQL limits.
It is also possible to set a different standard depending on the product or supplier. The boundaries are ultimately determined by the organization. This has to do with the vulnerability of the product, how critical is the product in terms of, for example, danger [gas valve] and what experience you have with a supplier. Linking your vendor rating to your AQL is therefore recommended. You will want to check suppliers who continuously deliver stable and high quality less often and adjust the test level accordingly. This does require regular reviews of the performance of your suppliers.

The defect levels generally used for most goods are: critical, major and minor. Critical defects are defects that are absolutely unacceptable, such as defects that could cause harm to the end user and / or defects that do not comply with [legal] regulations. Major defects are problems that make the product unacceptable to the end user. Minor defects are imperfections that deviate from specifications, but that end users are generally willing to accept.

For consumer goods, buyers typically set AQL limits of 0% for critical defects, 2.5% for major defects, and 4.0% for minor defects. These numbers are not rigid and can be adjusted as desired depending on the type of product or the relationship between the buyer and the manufacturer

AQL spreadsheet
In this article you will find an AQL spreadsheet that you can download and use for free. This sheet contains further explanation of how AQL works and how to use the spreadsheet. It contains both a tab for individual selections and Multi product selections. If you have any comments or questions about AQL or use of the spreadsheet, you can send an email to: Hans Groen

AQL one-line calculator

AQL applications

AQL calculation sheet – xlsx based.