Capability indices
Capability indices use estimated sigma .
Cp
Cp for one-sided specifications
If you are using one sided specifications, use the following formulas to determine the Cp:
Upper specification: |
Lower specification: |
Cr
Cpk
Where:
Zmin is the smaller of Zupper and Zlower.
Using estimated sigma:
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Cpm
Where: | ![]() |
T = specification target (nominal)
Xi = a given individual reading of " i "
n = total number of individual readings
= symbol for summation