Z94.16 - Quality Assurance & Reliability

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WARNING LIMITS (UPPER AND /OR LOWER).  In a Shewhart control chart, the limit below which (upper limit) or above which (lower limit) or the limits between which the statistic under consideration lies with a high probability when the process is under control.  Notes: (1) When the value of the statistic computed from a sample is outside the warning limits but inside the action limits, increased supervision of the process is generally necessary and rules may be made for action in particular processes. (2) At the warning limits, attention is called to the possibility of out-of-control conditions, but further action is not necessarily required. (3) The warning limits will always be within the action limits. [2: 3.4.4]

WEAR-OUT FAILURE PERIOD.  That final period, if any, in the life of an item during which the instantaneous failure intensity for a repaired item or the instantaneous failure rate for a non-repaired item is considerably higher then that of the preceding period.  [4: 191-10-10]

WITHIN-LOT (OR WITHIN-BATCH) VARIATION.  Dispersion of observatiions or test results obtained within a lot or batch.  Note: The within-batch variation may be estimated from a single batch or by pooling the estimates for several batches, as appropriate. [2: 3.1.3]

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