TABLE OF CONTENTS Acceptance sampling is used to distinguish between acceptable and unacceptable lots of raw materials and finished goods. One hundred percent (100%) inspection of an entire product lot of items such as spares and repair parts can be very expensive. Acceptance sampling determines acceptable and unacceptable lots based on a sample of the entire lot. It is a quality assurance technique used for inspecting both incoming materials and outgoing products. This technique is based on statistics in which a random sample will represent all of the items within a chosen lot.
Acceptance sampling is appropriate to use when:
Handling is likely to induce defects ( maintenance induced failures)
Inspection destroys the product ( destructive testing)
Time does not permit 100% inspection
Cost of misjudgment will be low
Inspection costs are high
Two types of errors can occur when acceptance sampling: A producer rejecting a good lot or a customer accepting a bad lot.
| Lot Satisfactory | Lot Unsatisfactory | |
|---|---|---|
| Reject lot | Type I error (producer's risk) - ? | Good (correct decision) |
| Accept lot | Good (correct decision) | Type II error (consumer's risk) - ? |
Acceptable Quality Level (AQL) is the smallest percentage of defects that will make the lot acceptable; a level that the customer prefers.
Producer's Risk ( ?) is the probability of rejecting equipment that has a true Mean Time Between Failure (MTBF) (see Appendix B) equal to the upper test MTBF. This is also known as a...
