How to Use the Process Capability Index to Improve Customer Satisfaction and Achieve Business Success

Before delivering your product or service to customers, it is essential to determine how well your process meets their specifications using the Process Capability Index (Cpk). It is crucial to address this question proactively instead of waiting for customer feedback regarding your performance.

Cpk is a measurable way to compare the Voice of the Customer (specifications, requirements, or customer expectations) with the Voice of the Process (control limits). Its objective is to determine a measurable indicator of whether you are meeting customer expectations.

Cpk considers customer specifications, process variation (standard deviation), and the mean's position relative to specifications. Reporting depends on whether the process mean has shifted towards the upper or lower specification limit to determine the minimum condition.

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The Cpk ratio can vary between 0 and any positive or negative number. A Cpk value greater than 1 signifies that the process is capable and operating within specifications, with the specification limit sufficiently distant. A Cpk value of 0 indicates that the distribution mean aligns with the specification, resulting in half of the process falling outside the specifications. A negative Cpk value suggests that the process mean is beyond the specification, resulting in more than 50% of the process being out of specification.

Difference between Cp and Cpk?

Cp is a metric for evaluating process capability, assuming the process is aligned with the specifications. On the other hand, Cpk considers any deviation in the process mean and is recommended when the process mean is not centred within the specifications.

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