A condition in which individual values are not predictable although they may come from a definable source.
The disserence between the highest and lowest values in a subgroup.
A consecutive number of points:
Consistently increasing or decreasing
Consistently above or below the center line.
A run of 7 consecutive points. Typically indicates an out-of-control condition.
A simple graphic representation of a characteristic of a process, showing plotted values of some statistic gathered from the process (often individual values) and a central line (often the median of the values) which can be analyzed for runs.
In process control applications, a synonym with Subgroup. This use is totally different from the purpose of providing an estimate of a larger group of people, items, etc.
The Greek letter used to designate Standard Deviation.
A source of variation that is intermittent, unpredictable, unstable. Sometimes called an Assignable cause. It is signaled by a point outside a control limit or a run or other non-random pattern of points within the control limits.
The engineering requirement for judging acceptability of a particular characteristic. A specification is never to be confused with a control limit.
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