The Westgard rules are a set of statistical patterns, each being unlikely to occur by random variability, thereby raising a suspicion of faulty
accuracy or precision of the measurement system. They are used for
laboratory quality control, in "runs" consisting of measurements of multiple samples. They are a set of modified
Western Electric rules
The Western Electric rules are decision rules in statistical process control for detecting out-of-control or non-random conditions on control charts. Locations of the observations relative to the control chart control limits (typically at ±3 stan ...
, developed by
James Westgard
James may refer to:
People
* James (given name)
* James (surname)
* James (musician), aka Faruq Mahfuz Anam James, (born 1964), Bollywood musician
* James, brother of Jesus
* King James (disambiguation), various kings named James
* Prince James ...
and provided in his books and seminars on quality control.
They are plotted on
Levey–Jennings chart
Laboratory quality control is designed to detect, reduce, and correct deficiencies in a laboratory's internal analytical process prior to the release of patient results, in order to improve the quality of the results reported by the laboratory. Qu ...
s, wherein the X-axis shows each individual sample, and the Y-axis shows how much each one differs from the
mean
A mean is a quantity representing the "center" of a collection of numbers and is intermediate to the extreme values of the set of numbers. There are several kinds of means (or "measures of central tendency") in mathematics, especially in statist ...
in terms of
standard deviation
In statistics, the standard deviation is a measure of the amount of variation of the values of a variable about its Expected value, mean. A low standard Deviation (statistics), deviation indicates that the values tend to be close to the mean ( ...
(SD). The rules are:
[ Review date: 1 April 2020]
The recommended consequences when any of the above patterns occur is to reject the run, except for the rule of 1
2s (top in table), which serves as a warning and a recommendation of careful inspection of the data.
[
]
See also
*Western Electric rules
The Western Electric rules are decision rules in statistical process control for detecting out-of-control or non-random conditions on control charts. Locations of the observations relative to the control chart control limits (typically at ±3 stan ...
*Nelson rules
Nelson rules are a method in process control of determining whether some measured variable is out of control (unpredictable versus consistent). Rules for detecting "out-of-control" or non-random conditions were first postulated by Walter A. Shewhar ...
References
External links
*{{official website, http://www.westgard.com/westgard-rules/
Quality control