How to Use AQL Sampling to Determine if Goods are Acceptable or Not? (Updated)

AQL Sampling Introduction

The Acceptance Quality Limit (AQL) is a standard for determining the quality of a product according to international standard ANSI ASQ Z1.4 It is the lowest acceptable quality level for a product, usually based on a percentage measurement.

During pre-shipment inspections, batches of products that do not meet the AQL will be rejected.

In this article, you will discover the AQL sampling methods and types of defects in products. With this in mind, you can detect these defects using an AQL chart to ensure customer satisfaction. Let’s get rolling!

How Does AQL Work?

First, an importer will randomly select a specific number of samples. They will inspect according to several standards like product quality and appearance. If the number of defects is less than a certain amount, the product fulfills AQL standard.

If the AQL standard is not fulfilled, AQI Service will explain the inspection results and notify the customer of the non-compliant defect problem. The manufacturers can correct the product based on the detective parts of the production process, according to the source of the problem.

Different products have different AQL judgment criteria. For instance, the electrical appliances are judged according to AQL 1.5 major defect and 4.0 minor defect, while groceries are judged according to AQL major 2.5 and minor 4.0.

Customers would want zero-defect products or services, yet it is unrealistic. Even the most professional manufacturers will create products with defects. However, the supplier can modify or remedy the defects to ensure that the whole batch of goods is close to zero defects.

Let’s discover further the type of AQL defects.

Types of AQL Defects

Defects happen when the products fail to meet the AQL. There are 3 categories of AQL defects, which are:

Critical Defects

Critical defects are products with 0% AQL, the most dangerous goods. In general, these products do not meet the basic regulations.

Major Defects

Major defects are products with 2.5% AQL and are usually not well received by the consumer. These defects will affect the experience of using the product.

Minor Defects

Minor defects are goods with 4% of AQL. These are defects that won’t reduce the usability of the product. Yet, its specifications are different from what you’ve requested.

How Do Experts Use An AQL Sampling Chart? Any AQL Calculator?

AQL Calculator from AQI Service
Click to Calculate sample size by AQL Calculator

An AQL sampling chart is an internationally accepted table for the quality control process. It helps you decide the sample size for inspection from your total order quantity and the acceptable defective units. All standardized charts have the same groupings and numbers.

Below are two examples of standardized charts and you can also calculated the specific AQL from our AQL Calculator quickly

AQL Sampling charts, sample size code letters

AQL Sampling charts, Single sampling plan for normal inspection

There are 4 steps to consider when using AQL chart for quality check as the AQL sampling guidelines:

1.   Type of Inspection & Level of Inspection

Your type of inspection will be either “general” or “special,” as shown in the first two columns of the table. “General” is usually the best option. “Special” is reserved for specific types of product testing. Those product checks need only a tiny part of your order to complete the AQL sampling.

Each inspection type consists of many inspection levels. Higher inspection levels represent a more extensive scope and contribute to a larger sample size in the columns to the left. For general inspection, there are three AQL sampling levels, which are:

G-I Level

This budget option offers the smallest sample size, yet the products pose few safety risks. You should only use it when you are just starting and have budget constraints.

Besides, only choose GI level when you strongly trust your supplier and have a small lot size.

G-II Level

It can cover a broader scope at a low price, hence the most chosen option. The sample size is usually enough to ensure specified quality.

The G-II inspection level is suitable for the first round of inspection. Then, you can decide whether G-II is still a good fit in the future. If not, you should determine whether to raise or lower your inspection level.

G-III Level

It provides the largest sample size, nearly four times larger than the sample size of the G-I level. The inspection cost for the G-III Level is also relatively high.

This level has the greatest quality assurance and you’ll be less likely to receive orders with many defective pieces. You should choose it when your supplier has a poor track record of quality control or if you are importing luxury products or medical devices.

Overall, most general inspections fall under the “G-II” category. For a limited budget or those not needing a thorough inspection, you should choose “G-I” with a smaller inspection sample size. Those who care more about quality should choose “G-III” for a larger sample size.

2.   Sample Size Letter

The quantity of every item in your order is the lot size. Inspecting large lot sizes separately can increase the time and cost of the inspection. You might want to combine similar products to inspect them together through AQL sampling.

In the first AQL chart, a letter appears where your lot size row and inspection level column meet and intersect. This letter is your “sample size letter” representing a sample size in the second AQL chart. You’ll use this along with your acceptable quality level to determine how many products you should pull out at random for inspection.

3.   Acceptable Quality Levels for Inspection

Acceptable quality levels are at the top of the second part of the AQL chart, with sample size code letters running down the left column.

Your AQL represents your tolerance for quality defects. Higher AQL’s indicate a greater tolerance, and lower AQLs mean less tolerance for flaws. You should decide the number of defects you’re willing to accept in a single batch of orders.

During AQL sampling, there are unique AQLs for quality defects classified as critical, major, or minor. You will use an AQL of 0% for minor defects, 2.5% for major defects, and 4% for critical defects.

4.   Acceptance & Rejection Points

Each AQL column divides into two columns. These are your points of acceptance and rejection. If the number of defects found exceeds your acceptance point, the order should be rejected based on your chosen AQL.

When matching your original sample size to your chosen AQL, you may notice an arrow pointing up or down in place of acceptance and rejection points. An arrow pointing down shows that you’ll need a larger sample size than you estimated based on your lot size. An arrow pointing up shows that your original lot size is excessive, and a smaller sample size is needed.

When to Use AQL Sampling?

There are times when AQI sampling saves more time and cost compared to other quality control methods. Here are the situations where you should use AQL sampling:

Large Lot Sizes

For all importers, it is unrealistic to carry out a 100% inspection on every product. It is where AQL sampling comes into place to inspect products with larger lot sizes. Although not guaranteed, most of your products will be up to requirements.

Automated Manufacturing Process

AQL sampling is more effective, accurate, and consistent using machines. Most products share the same quality, as it’s easier to identify rejected orders. Besides, it reduces the risk of human error as it requires less manual labor.

Final Thoughts

AQL sampling is beneficial in determining the quality of goods before they are shipped. Using this sampling method can provide insights into your manufacturer. Once defects are found, it is essential to fix them.

Through product quality inspection, you would be able to provide your customers with better products. You can also intuitively feel the quality level of the product batch via the inspection reports. A good product can not only help you improve your sales performance but also maintain your company’s reputation.

This article gives you all the information you need about AQL sampling. If you need to inspect whether your product is high quality, you can contact us. Or, if you have any questions about the AQL guidelines, please leave a message in the comment area, and we’ll answer them for you.

More articles about how to use AQL Table:

Author: AQI Service is a professional quality control service company in China specialized in providing a complete range of quality inspection and testing certification services in China & Asia for global importers, buyers, retailers, and sellers.