Formulas and Tables

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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



Cpm
Where: | ![]() |
T = specification target (nominal)
Xi = a given individual reading of ” i ”
n = total number of individual readings
= symbol for summation