A tolerance interval or proportion of a performance distribution derived from the measurement of a significant number of units. The quantity of a parameter covered by a specification, but over a narrower range of conditions. For example, a specification describes the performance of a parameter over the 0 to 50 C temperature range. A characteristic may describe the same parameter but over the 20 to 30 C temperature range. The user documentation shipped with a product from the factory includes the verification procedures and clearly differentiate calibration procedures from function tests.
Function tests are quick tests designed to verify basic operation of a product.
Function tests include operator's checks and operation verification procedures. An operator's check is normally a fast test used to verify basic operation of a product. An operation verification procedure verifies some, but not all, specifications, and often at a lower confidence level than a calibration procedure. An operator's check performs a basic functional test of a product, use minimal test equipment and are run on a regular basis by the user of the product. The purpose of operational verification tests is to verify instrument operation quickly with reasonable confidence.