Cpm is one of several indices used to measures Process Capability. Cpm is called the Taguchi Capability Index. It combines variability and distance from the target into one measure and is closely related to the Taguchi 'Signal to Noise Ratio' concept:
Where:
USL, LSL

Upper and Lower Specification Limits 
T

Target value 
σ

Process Standard Deviation 
μ

Process Mean 
