Capability of a process, as judged by the historical records, shows the probability of the process to achieve the desired results. Capability analysis is important as it helps to maintain a constant improvement in the process, and also helps decide if the customer’s specifications can be met.
Capability analysis can be done both visually and mathematically. What is important, is to find the tools that can compare the actual performance of a process to the defined standards.
The two indices which are required to understand the capability of a system are ‘Cp’ and ‘Cpk’. Simply put, Cp is a measure of how capable your process is. Reducing the variation in a process, brings it closer to being what it should ideally be. It would then have a higher Cp.
Cpk takes the off-centeredness into account, which means it helps do the capability analysis if the process mean falls outside the specification limits.