The

**capability index**of a process measures the percentage of non-conforming values produced by the process. Denoted as C_{pk}, it is defined as:**C**= min[ (USL – mean) /3σ , (mean – LSL) /3σ ]

_{pk}where

*USL*is the upper specification limit*LSL*is the lower specification limit*mean*is the process mean*σ*is the process standard deviation

To find the process capability index, simply fill in the values below and then click the “Calculate” button.

Capability Index (C_{pk}): **0.4505**

**Explanation:**

C_{pk} = min[ (USL – mean) /3σ , (mean – LSL) /3σ ]

C_{pk} = min[ (17– 12) /3*3.7 , (12– 6) /3*3.7 ]

C_{pk} = **0.4505**