2. What about capability indicators?

The previous step introduced the concept of random phenomena. Any manufacturing process is an example of random phenomena disturbed by numerous factors which are themselves random. It is therefore legitimate to assume, initially, that the manufacturing process can be modeled by a normal distribution. The next step is to ensure that the process is indeed capable of producing a given quantity (often a large quantity, of course) of products that meet the customer's requirements. Non-conforming" products are part of what we call "customer risk", a risk that the customer is prepared to accept.

Analysis of a process's ability to produce a sufficient number of conforming items is known as a "Capability Study". It consists in ensuring that the manufacturing process does not disperse too much with regard to the tolerance required by the customer, and that it is sufficiently...