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# Z94.16 - Quality Assurance & Reliability

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RANDOM VARIABLE.  A variable that may take any of the values of a specified set of values and with which is associated a probability distribution. [1: 1.2]

RANDOMIZATION.  The process by which a set of items are set into a random order.  Note: If, from a population consisting of the natural numbers 1 to n, numbers are drawn at random (i.e. in such a way that all numbers have the same chance of being drawn), one by one successibely, without replacement, until the population is exhausted, the numbers are said to be drawn' in random order".  If these n numbers have been associated in advance with n distinct objects or n distinct treatments which are then rearranged in the order in which the numbers are drawn, the order of the objects or treatments is said to be randomized. [1: 2.91]

RANGE.  The difference between the largest and the smallest observed value of  a quantitative characteristic. [1: 2.30]

RANGE CHART; R CHART.  A control chart for evaluating the variability within a process in terms of the range of the sub-group. [2: 3.3.13]

RATIONAL SUB-GROUP.  In an ordered sequence, one of the sub-groups within which variations may be considered to be due to non-assignable chance causes only, but between which there may be variations due to assignable causes the presence of which is considered both possible and important to detect. [2: 1.3.11]

RECTIFYING INSPECTION.  Removal or replacement of nonconforming items during inspection of all the items (or of some specified number of items) in a lot or batch which was not accepted by acceptance sampling.  [2: 1.2.7]

REDUNDANCY.  In an item, the existence of more than one means for performing a required  function. [4: 191-15-01]

REDUNDANCY, ACTIVE.  That redundancy wherein all means for performing a required function are intended to operate simultaneously. [4: 191-15-02]

REDUNDANCY, STANDBY.  That redundancy wherein a part of the means for performing a required function is intended to operate while the remaining parts of the means are inoperative until needed.[4: 191-15-03]

RELIABILITY (OF AN ITEM, EXPRESSED NUMERICALLY).  The probability that an item will perform a required function under stated conditions for a stated period of time.  Note:  This definition is used when defining the characteristic intended by such modified terms as "assessed reliability" and "predicted reliability."  [4: 191-12-01]

RELIABILITY  (GENERAL DEFINITION).  Ability of an item to perform a required function under stated conditions for a stated period of time. [4: 191-02-06]

RELIABILITY, HUMAN PERFORMANCE.  The probability that man will accomplish all required human functions under specified conditions. [7]

RELIABILITY, INHERENT.  The potential reliability of an item present in its design.

REJECTABLE PROCESS LEVEL (RPL).  A process level which forms the inner boundary of the zone of rejectable processes. [2: 3.4.11]

REJECTION NUMBER, RE; NON-ACCEPTANCE NUMBER.  In sampling inspection by attributes, the smallest number of nonconformities or nonconforming items found in the sample that requires that the lot be not accepted, as given in the sampling plan. [2: 2.3.11]

REPEATABILITY.  Precision under repeatability conditions. [1: 3.15]

REPEATABILITY CONDITIONS.  Conditions where independent test results are obtained with the same method on identical test items in the same laboratory by the same operator using the same equipment within short intervals of time.[1: 3.16]

REPEATABILITY STANDARD DEVIATION.  The standard deviation of test results obtained under repeatability conditions.  Notes: (1) It is a measure of the dispension of the distribution of test results under repeatability conditions. (2) Similarly "repeatability variance" and "repeatability coefficient of variation" could be defined and used as measures of the dispension of test results under repeatability conditions. [1: 3.17]

REPETITION.  A term denoting the execution of a statistical inquiry several times using the same method on the same population under the same conditions.  [1: 2.89]

REPLICATION.  During the course of an experiment or survey, replication is the determination a a value more than once.  Note: Replication should be distinguished from repetition by the fact that replication denotes determinations carried out at different places and/or times defined in the plan or design.  The successive determinations, including the first, are called replicates.   [1: 2.90]

REPRODUCIBILITY.  Precision under reproducibility conditions. [1: 3.20]

REPRODUCIBILITY CONDITIONS.  Conditions where test results are obtained with the same method on identical test items in different laboratories with different operators using different equipment. [1: 3.21]

REPRODUCIBILITY STANDARD DEVIATION.  The standard deviation of test results obtained under reproducibility conditions.  Notes: (1) It is a measure of the dispension of the distribution of test results under reproducibility conditions. (2) Similarly "reproducibility variance" and "reproducibility coefficient of variation" could be defined and used as measures of the dispension of test results under reproducibility conditions. [1: 3.22]

RUN.  In a series of observations of a qualitative characteristic, the occurrence of an uninterrupted series of the same attribute is called a "run". In a series of observations of a quantitative characteristic, a consecutive set of values which are monotonically increasing or decreasing is said to provide a run "up" or "down" respectively. [1: 2.48]

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