Statistical process control (SPC) is an approach to process control that has been widely used
in any industrial or non-industrial fields.
SPC is based on so called Shewhart´s conception of the process variability. This conception
distinguishes variability caused by obviously effected common causes (process is
considered to be statistically stable) from variability caused by abnormal assignable causes
(process is considered not to be statistically stable).
The main goals of SPC is an identification of abnormal variability caused by assignable
causes with the aim to
1. make the process stable,
2. minimize the process variability,
3. improve the process performance (see Fig. 1.)