Familiarize With AQL Table: The Basics Of Quality Control Techniques

Generally, the standards ISO2859, BS6001, ANSI/ASQZ1.4, DIN40080 Sampling Procedures, and Tables for Inspection by Attributes are adopted for the performance of inspections. Although with different codes, these standards describe very much the same rules.

Sampling, multiple sampling inspection in which, after each sample is inspected, the decision is made to accept a lot, reject it, or take another sample. But there is a prescribed maximum number of samples, after which a decision to accept or reject the lot must be reached.

Sampling, double sampling inspection in which the inspection of the first sample leads to a decision to accept a lot, reject it, or take a second sample; the inspection of a second sample, when required, then leads to a decision to accept or to reject the lot.

A sampling at random is commonly used in acceptance sampling theory, the process of selecting sample units so all units under consideration have the same probability of being selected.

An acceptable method of random selection with equal probabilities is the use of a table of random numbers in a standard, A military standard that describes the sampling procedures and tables for inspection by attributes.

Inspection tightened inspection by a sampling plan that has stricter acceptance criteria than those used in normal inspection. Tightened inspection is used in some inspection systems as a protective measure when the level of submitted quality is sufficiently poor. The higher rate of rejections is expected to lead suppliers to improve the quality of the submitted product.

Inspection reduced inspection by a sampling plan requiring smaller sample sizes than those used in normal inspection. Reduced inspection is used in some inspection systems as an economic measure when the level of submitted quality is sufficiently good and other stated conditions apply.

Inspection, normal inspection used by a sampling plan under ordinary circumstances.

Acceptable Quality Level (AQL):

The acceptable level (AQL) is defined as the maximum percent defective that, for purpose of sampling inspection, can be considered satisfactory as a process average.

Inspection Levels:

The standards provide for three general inspection levels and four special inspection levels. These seven levels permit the user to balance the cost of inspection against the amount of protection required.

There are two AQL tables. The first one tells you which 'code letter' to use based on the selected sample plan, such as S1, S2, GII, GIII, etc., with GIII being the most stringent testing, the GII is the standard and is most commonly used.

The Sampling Plan Tables(Sample Size Code Letters and Acceptable Quality Level-Normal Inspection) are incorporated into international quality standards to help and ensure you puechased products quality meet your expectations.It will decide the sampling size according to your  purchased goods order quantity and your Acceptable Quality Level ,Most of the product inspection sampling plan used is Level 2  or GII.

If your order has multiple items, the ideally perform the product inspect as Level 2/GII inspection for per item, if you do not want to take additional risks. If inspect as general Level 2 or GII sampling size on multiple items orders, and per item sampling size is assigned according to the per item quantity proportion, increasing the risks as the sampling size was not be representative enough.

To find the sampling size for inspection, we look at the below left chart:the range of total items produced quantity on the left side(Lot or batch size) of chart & SpecialInspection Levels and General Inspection Levels. the choice of GI, GII, and GIII at General Inspection Levels, with GIII being the most stringent testing and GI being the least. GII is the standard and most commonly used. For example, if you are booking 8,000 units, choice the GII that results in the letter L which in turn corresponds to the inspection of 200 units in the second table.On the top of the second AQL chart, you can find the defect levels, ranging from 0 to 10 Choose which level to apply to each type of defect: Critical/Major/ Minor. Most importers usually choose standard defect AQL:0/2.5/4.0 & 0/1.5/4.0, but you can pick 0/1.0/1.0 or 0/1.5/2.5 for high-risk products such as those in the automotive industry. if using the standard 0/2.5/4.0 defect AQL and sample size of 200, we see that if you have more than 0 critical defects, 10 major defects, or 14 minor defects, you should reject your shipment. Of course, the decision about what to do after you received the inspection results belongs to you. Most importers discuss all inspection findings with their vendor/manufacturer to improve wherever possible.In case the inspection results are very close to AQL limits, it is important that you double-check if the level of found defects is acceptable to you or not.