Cpk Value differs between QC-CALC and Stat Package
This article explains the different Cpk standards available.
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written: 03/02/2006
last modified: 03/22/2024


The Cpk value that I see in the reports is different than the Cpk value that my other stat package shows. Why do the Cpk values not agree?


There are two different standards when it comes to these calculations and QC-CALC is probably not defaulting to the standard you are expecting.


There are 2 different sets of standards for these calculations and QC-CALC follows the standards supported by ASQ. The other common standard is AIAG and instead of showing a Cpk value a Ppk value is used. In the Tools – Options – Global – Other section there is a checkbox that will switch to the AIAG standard. Check the Show Ppk instead of Cpk box and you will now see Ppk throughout the program.


For more information about the differences between the standards and between Cpk and Ppk please see the white paper on this subject.

Applies To

QC-CALC Real-Time v.4.10
QC-CALC Real-Time v.4.00
QC-CALC Real-Time v.3.40
QC-CALC Real-Time v.3.30
QC-CALC Real-Time v.3.20
QC-CALC Real-Time v.3.00
QC-CALC SPC v.4.10
QC-CALC SPC v.4.00
QC-CALC SPC v.3.40
QC-CALC SPC v.3.30
QC-CALC SPC v.3.20
QC-CALC SPC v.3.00