Inspection — The process of measuring, examining, testing or otherwise comparing the unit of product with the requirements.
Inspection by attributes — The 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 of requirements.
Lot or batch — Means “inspection lot” or “inspection batch”, i.e., a collection of units of product from which a sample is to be drawn and inspected and differ from a lot or batch for other purposes (e.g., production, shipment, etc.).
Lot or batch size — The number of units of product in a lot or batch.
Sample — A sample consists of one or more units of product drawn from a lot or batch, the units of the sample being selected at random without regard to their quality. The number of units of product in the sample is the sample size.
AQL — Acceptable quality level. 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.
Sample size code letter — A device used along with the AQL for locating sampling plan on the table of sampling plans.
Sampling plan — A sampling plan indicates the number of units of product from each lot or batch which are to be inspected (sample size) and the criteria for determining the acceptability of the lot or batch (acceptance and rejection numbers).
Inspection procedures — Normal inspection will be used at the start of inspection. Normal, tightened or reduced inspection shall continue unchanged for each class of defects or defectives on successive lots or batches except where the switching procedures given below require change.
Inspection level — The inspection level determines the relationship between the lot or batch size and the sample size. The inspection level to be used for any particular requirement will be as prescribed by the contractor’s written procedures. Three inspection levels: I, II, III, are given in Table I for general use. Normally, Inspection Level II is used.
Types of Sampling plans — Three types of sampling plans: Single, Double, and Multiple, are given in table II, III, and IV, respectively… The average sample size of multiple plans is less than for double, … , and both of these are always less than a single sample size. Usually the administrative difficulty for single sampling and the cost per unit of the sample are less than for double or multiple.
Determination of Acceptability (Single Sampling Plan) — The number of sample units inspected shall be equal to the sample size given by the plan. If the number of defectives found in the sample is equal to or less than the acceptance number, the lot or batch shall be considered acceptable. If the number of defectives is equal to or greater than the rejection number, the lot or batch shall be rejected.
Defect — A defect is any nonconformance of the unit of product with specified requirements.
Defective — A defective is a unit of product which contains one or more defects.
Critical — A defect that could cause injury to the user due to unsafe or hazardous conditions.
Major — A defect or failure that will cause the product not to perform its tactile function or not perform within its specifications. Major also include cosmetic defects that are not saleable.
Minor — A defect that does not affect the usability or salability of the product.