The formula to calculate the CPK (Process Capability Index) is:
\[ CPK = \min\left(\frac{USL - \text{mean}}{3 \cdot \text{std}}, \frac{\text{mean} - LSL}{3 \cdot \text{std}}\right) \]
Where:
CPK is defined as the process capability index and is a measure of the ability of a process to produce objects to a customer's specifications.
Let's assume the following values:
Using the formula to calculate the CPK:
\[ CPK = \min\left(\frac{10 - 6}{3 \cdot 1}, \frac{6 - 2}{3 \cdot 1}\right) = \min\left(\frac{4}{3}, \frac{4}{3}\right) = 1.33 \]
The CPK is 1.33.