Processes are parts of a system. With this in mind, a process may be more specifically defined as:
A set of interrelated activities which transform a set of inputs to one or more outputs.
All the inputs will vary. This variation combines and interacts within the process. Variation in outputs is therefore the complex sum of all this variation. Much effort is wasted analysing the outputs of processes. It is the understanding, reduction, and control of input and process variation which is at the heart of ongoing and sustainable improvement.
There are many reasons for this continuing variation. These reasons can, however, be broken down into two different types, which are: