What are the measures of process capability?

These indices show what the process is "capable" of doing. This is the six sigma range of the inherent variation of a statistically stable process. Sigma is estimated using the /d2 formula.

>Cpk
>Cp
>Cr
>Cpm

What are the measures of process performance?

These indices show what a process is actually doing. This is the six sigma range of the total process variation, where sigma is usually determined by the sample standard deviation.

>Ppk
>Pp
>Pr