A distinguishing feature of a process or its output on which variables or attribute data can be collected.
A source of variation that affects all the individual values of the process output being studied. In control chart analysis it appears as part of the random process variation.
Units of output produced in succession. A basis for selecting subgroup samples.
A graphic representation of a characteristic of a process showing plotted values of some statistic gathered from that characteristic, a center line, and 1 or 2 control limits. It has two basic uses:
As a judgement to determine is a process has been operating in statistical control, and
As an operation to aid in maintaining statistical control.
A line (or lines) on a control chart used as a basis for judging the significance of variation from subgroup to subgroup. Variation beyond a control limit is evidence that special causes are affecting the process. Control limits are calculated from proce
A past-oriented strategy that attempts to identify unacceptable output after it has been produced, and then to separate it from the good output.
A way of describing the output of a common-cause system of variation in which individual values are not predictable but in which the outcomes as a group form a pattern that can be described in terms of its location, spread and shape. Location is commonly
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