If a processes mean, or average, is shifted
with respect to the design or specification mean, the inherent process
capability is adjusted with a factor k, and becomes Cpk.
Specification Width / 2
Note: in some
industries this calculation is called Ppk.
This is the capability of the process
expressed in relation to a worse case scenario view of the data. It is
denoted by the symbol Cpk.
Use it to determine if a process or
service, is within the normal variation,
and is capable of meeting specifications.
Cpk = the lesser of ...
Spec Limit - Mean)
- Lower Spec Limit )
Note: s = Sigma
For an example of a distribution,
X Bar, and R Bar
charts see our ZeroRejects
features page. It makes doing statistical
process control charts easy. And at only $150.00, (USD), our
software can get you going quickly.
Also see Cpk
vs PPM, Common
cause. Our free
software can do Cpk, along with PPM and yields, for you.
We have a free and commercial product to
aid you in these calculations for discrete
data types. See the free
Cpk calculator and the commercial
Cpk calculator for more details.