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Cpk
index
A Process Capability Index.
A measure of both process dispersion and its centering about the average.
Cpk= MIN[Cpu , Cpl]
where
Cpu = zUSL / 3
Cpl = - zLSL / 3
For Normal Distributions, the z-value for the USL and LSL are calculated as:
zUSL=(USL-GrandAverage)/ProcessSigma
zLSL=(GrandAverage-LSL)/ProcessSigma
For Non-Normal Distributions, the z-value for the USL and LSL are calculated by estimating the percent of the fitted distribution
beyond each specification limit, then converting those percentages to z-values for the Normal distribution.
See also:
Process
Capability Charts
Confidence
Intervals for Cpk
Cp
Cr
Cpm
Process
Performance
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