Z94.16 - Quality Assurance & Reliability

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CAPABILITY.  The ability of an item to meet a service demand of given quantitative characteristics under given interval conditions. [4: 191-02-04]

CHAIN SAMPLING INSPECTION.  Sampling inspection in which the criteria for acceptance of the current lot are governed by the sampling results of that lot and those of a specified number of the preceding consecutive lots. [ 2: 2.4.8]

CHARACTERISTIC.  A property which helps to identify or differentiate between items of a given population. [2: 1.51]

CHANCE CAUSES.  Factors, generally many in number but each of relatively small importance, contributing to variation, which have not necessarily been identified.  Note: Chance causes are sometimes referred to as common causes of variation.[2: 3.1.9]

COEFFICIENT OF VARIATION.  For a non-negative characteristic the ratio of the standard deviation to the average.  Notes: (1) The ratio may be expressed as a percentage. (2) The term "relative standard deviation" is sometimes used as an alternative to "coefficient of variation", but this use is not recommended. [1: 2.35]

CONFIDENCE LIMIT.  Each of the limits, T1 and T2, of the two-sided confidence interval or the limit T of the one-sided confidence interval. [1: 2.60]

CONFORMITY.  Fulfilment of specified requirements.  Note: The above definition is valid for the purposes of quality standards.  The term "conformity" is defined differently in ISO/IEC Guide 2. [3: 2.9]

CONSUMER'S RISK (CR).  For a given sampling plan, the probability of acceptance of a lot or process when the quality level (e.g. fraction nonconforming) has a value stated by the plan as unsatisfactory [e.g. a limiting quality level (LQL)]. [2: 2.6.4]

CONSUMER'S RISK QUALITY (CRQ).  A lot or process quality level which in the sampling plan corresponds to a specified consumer's risk.  Notes: (1) The type of operating characteristic curve should be specified. (2) A special case of this is "limiting quality level" when the operating characteristic curve is of type B. [2: 2.6.6.]

CONSUMER'S RISK POINT (CRP).  A point on the operating characteristic curve corresponding to a predetermined and usually low probability of acceptance.   Notes: (1) This probability of acceptance is called the "consumer's risk" and the corresponding lot quality determined by the CRP for the risk is called the 'consumer's risk quality (CRQ)'. (2) The type of operating characteristic curve should be specified.  [2: 2.6.5]

CONTROL CHART.  A chart, with upper and/or lower control limits, on which values of some statistical measure for a series of samples or sub-groups are plotted, usually in time or sample number order.  The chart frequently shows a central line to assist detection of a trend of plotted values toward either control limit.  Note: In some control charts, the control limits are based on the within-sample or within-sub-group data plotted on the chart; in others, the control limits are based on adopted standard or specified values applicable to the statistical measures plotted on the chart.  [2: 3.3.1]

CONTROL CHART FACTOR.  A factor, usually varying with sample size, to convert specified statistics or parameters into a central line value or control limit appropriate to the control chart. [2: 3.4.6]

CONTROL LIMITS:  SHEWHART CONTROL LIMITS (UPPER AND/OR LOWER).  In a 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 very high probability when the process is under control.  [2: 3.4.1]

CONTINUOUS SAMPLING INSPECTION.  Sampling inspection intended for application to a continuous flow of individual items of product that (a)involves acceptance or non-acceptance on an item-by-item basis, and (b)uses alternate periods of 100% inspection and sampling depending on the quality of the observed product. [2: 2.4.5]

CORRECTIVE ACTION.  Action taken to eliminate the causes of an existing nonconformity, defect or other undesirable situation in order to prevent recurrence.  Notes: (1) The corrective actions may involve changes, such as in procedures and systems, to achieve quality improvement at any stage of the quality loop. (2)There is a distinction between "correction" and "corrective action": "correction" refers to repair, rework or adjustment and relates to the disposition of an existing nonconformity; "corrective action" relates to the elimination of the causes of a non-conformity. [3: 4.14]

CORRELATION.  The relationship between two or several random variables within a distribution of two or more random variables.  Note: Most statistical measures of correlation measure only the degree of linear relationship. [1: 1.13]

COUNT CHART; C CHART.  A control chart for evaluating the process in terms of the count of nonconformities of a given classification occurring in the sample.  [2: 3.3.5]

COUNT PER UNIT CHART (U-CHART).  A control chart for evaluating the process in terms of the average count of nonconformities of a given classification per unit occurring within a sample. [2: 3.3.6]

COVARIANCE.  The sum of the products of the deviations of x and y from their respective averages divided by one less than the number of observed pairs:

(FORMULA MISSING)

CURTAILED INSPECTION.  A sampling procedure which contains a provision for stopping inspection when it becomes apparent that adequate data have been collected for a decision. [2: 2.5.7]

CUMULATIVE SUM CHART; CUSUM CHART.  A control chart on which the plotted value is the cumulative sum of deviations of successive sample statistics from a target value.  When a process change is made, the sum is returned to zero.  The ordinate of each plotted point represents the algebraic sum of the previous ordinate and the most recent deviation from the target.  Note: Cusum charts are generally interpreted by masks superimposed on the chart, a signal occurring if the path of the cusum intersects or touches the boundary of the mask. [3.3.12]

CRITICAL VALUE.  The limiting value of the critical region. [1: 2.72]

CRITICAL REGION.  The set of values of the test statistic for which the null hypothesis is rejected.  Note: Critical regions are determined in such a way that if the null hypothesis is true, the probability of this null hypothesis being rejected should be not more than a given value a which is in general low (for example 5% or 1%). [1: 2.71]

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