
The absence of special causes of variation. The state of being in statistical control.
A process which is in statistical control.
A measure of the spread of the process output or the spread of a sampling statistic from the process (e.g., of subgroup averages). Denoted by the Greek letter sigma ( s ).
A value calculated from or based upon sample data (e.g., a subgroup average or range), used to make inferences about the process that produced the output from which the sample came.
The condition describing a process from which all special causes of variation have been eliminated and only common causes remain. This is evidenced on a control chart by the absence of points beyond the control limits and by the absence of nonrandom pat
The use of statistical techniques such as control charts to analyze a process or its output so as to take appropriate actions to achieve and maintain a state of statistical control and to improve the process capability.
One or more events or measurements used to analyze the performance of a process. Rational subgroups are usually chosen so that the variation represented within each subgroup is as small as feasible for the process (representing the variation from common
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