It seems like most suppliers and most buyers can only remember “AQL 2.5” when it comes to the settings of QC inspections. Unfortunately, “Sampling as per AQL 2.5” means nothing.

I am aware that “single sampling plan by attributes as per the ISO 2859-1 standard, normal severity, level II” is a bit difficult to remember. But that’s what determines the number of samples to pick.

Here is the table that matters:

How to read this table? 

If you follow my example, I assume your ‘lot size’ is comprised between 3,201 pcs and 10,000 pcs, and that your inspection level is ‘II’. Consequently, the code letter is “L”.

By contrast, the AQL, or Acceptance Quality Limits, are settings that indicate what number of defects is over the client’s tolerance. These settings do not impact the number of samples an inspector has to pick.

The second table comes into play:

How to read this table?

Your code letter is “L”, so you will have to draw 200 pcs randomly from the total lot size.

Besides, I assume you have set your AQL at 2.5% for major defects and 4.0% for minor defects. Therefore, here are the limits: the products are accepted if NO MORE than 10 products with major defects AND NO MORE than 14 products with minor defects are found.

I hope I clarified this subject. Hearing incorrect descriptions of inspection settings is a pet peeve of mine.