This publication establishes lot or batch sampling plans and procedures for inspection by
attributes.This publication shall not be interpreted to supercede or conflict with any contractual requirements.
The words "accept","acceptance","acceptable",etc,refer only to the contractor's use of the sampling plans
contained in this standard and do not imply an agreement by the Government to accept any product. Determination
of acceptability by Government to shall be as described in contractual documents.The sampling plans described in
this standard are applicable to AQL's of .01 percent or higher and are therefore not suitable for applications
where quality levels in the defective parts per million range can be realized.
3.1 Acceptable Quality Level (AQL) .
When a continuous series of lots is considered,the AQL is the quality level
which, for the purposes of sampling inspection, is the limit of a satisfactory process average(See 3.19). NOTE: A
sampling plan and an AQL are chosen in accordance with the risk assumed. Use of a value of AQL for a certain
defect or group of defects indicates that the sampling plan will accept the great majority of the lots or batchs
process average level of percent defective(or defects per hundred units) in these lots or batches be no greater
than the designated value of AQL. Thus, the AQL is a designated value of percent defective(or defects per hundred
units) for which lots will be accepted most of time by the sampling procedure bing used. The sampling plans
provided herein are so arranged that the probability of acceptance at the designated AQL value depends upon the
sample size,being generally higher for large samples than for small ones,for a given AQL. The AQL alone does not
identify the chances of accepting or rejecting individual lots or batches but more
directly relates to what might be expected from a series of lots or batches,
provided the steps indicated in this publication are taken. It is necessary to refer to the operating
characteristic curve of the plan to determine the relative risks.
3.5 Critical Defect.
A critical defect is a defect that judgement and experience
indicate would result in hazardous or unsafe conditions for individuals using,
maintaining,or depending upon the product,or a defect that judgement and
experience indicate is likely to prevent performance of the tactical funtion of a
major end item such as a ship,aircraft,tank,missile,or space vehicle.
A defect is any nonconformance of the unit of product with specified requirements.
Inspection is the process of measuring,examining,testing,or otherwise comparing the unit of
product with the requirements.
3.11 Inspection by Attributes.
Inspection by attributes is inspection whereby either the unit of product is
classified simply as defective or non-defective, or the number of defects in the unit of product is counted,with
respect to a given requirement or set or requirements.
3.14 Major Defect
A major defect is a defect,other than critical,that is likely to result in failure,or to
reduce materially the usability of the unit of product for its intended purpose.
3.16 Minor Defect
A minor defect is defect that is not likely to reduce materially the usablity of the unit of
product for its intended purpose,or is a departure from established standards having little bearing on the
effective use of operation of the unit.
3.19 Process Average
The process average is the average percent defective or average number of defects per
hundred units(whichever is applicable) of product submitted by the supplier for original inspection.Original
inspection is the first inspection of particular quantity of product as distinguished from the inspection of
porduct which has been resubmitted after prior rejection.
A sample consists of one or more units of product drown from a lot or batch, the units of the sample
being selected at random without regard to hteir quality. The number of units of product in the sample is the
3.21 Sample Size Code Letter
The sample size code letter is a device used along with the AQL for locationg a
sampling plan on a table of sampling plans.
3.22 Sampling Plan
A sampling plan indicates the number of units of product from each lot or batch which are to
be inspectied (sample size or series of sample sizes) and th cirteria for determining the acceptability of the
lot or batch(acceptance and rejection numbers).