Quality Advisor℠

Your proof of quality® resource

Capability indices

Capability indices use estimated sigma .

Cp

cp formula

Cp for one-sided specifications

If you are using one sided specifications, use the following formulas to determine the Cp:

Upper specification:

cpu formula

Lower specification:

cpl  formula

Cr

cr formula

Cpk

cpk formula

Where:

Zmin is the smaller of Zupper and Zlower.

Using estimated sigma:

z upper formula z lower formula

Cpm

cpm formula

Where: sigma for cpm

T = specification target (nominal)

Xi = a given individual reading of " i "

n = total number of individual readings

= symbol for summation

Free monthly quality tips

FREE Newsletter on training tips, statistical help, book reviews and new product informationSubscribe to our free monthly newsletter, Quality eLine. It offers quality improvement information, quality training tips, statistical process control help, gage R&R information, and more.

Subscribe

Easily perform
capability studies with

Join the pack today!

Learn more   Try it!