The Cp value of 1.43 calculated for the process shows that the natural process spread will fit comfortably within the customer's specified tolerance. However, this is not the end of the story. The value of Cp only tells you whether the process could potentially meet the customer's specification, it does not consider whether the process is also well-centred with respect to the customer's specification.
You will recall from the section on capability (or you may like to refer back to it), that it is quite possible for a process with a good Cp value still to produce product that falls outside the specification limits. To check for this situation, it is necessary to calculate a different capability index, Cpk.
Cpk takes into account both: