Levey-Jennings Chart
The Levey–Jennings chart is a type of statistical process control (SPC) chart, typically used in laboratory quality control applications.
It differs from the traditional Shewhart individuals control chart because it uses the long-term (overall or population) estimate of sigma instead of the short-term (i.e., within subgroup or sample) estimate of sigma.
For proportion data, it uses 10-20-30 percent for the control limits.
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Instead of using the Nelson Rules, it is recommended to use the Westgard Rules to detect whether the results from the samples when the control was done can be released, or if they need to be rerun.
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