SPC is a method for continuously improving
processes and products. SPC is an abbreviation of Statistical
Process is understood to refer to any repetitive operation.
The SPC method is thus also applicable, for instance, to procurement,
sales, engineering, research and development, production and
- as proof of quality production,
- process control and
- systematic diagnosis for the analysis and solution of
problems with the purpose of continuous quality improvement.
The control card technique is an important tool for SPC.
A process that displays only natural variability is stable
and predictable. Such a process is, in other words, under
statistical control. A process of this type is an important
precondition for achieving the highest quality. A process
that also contains unnatural variability is unstable and unpredictable.
Such a process is not under statistical control. The unnatural
variability occurs without warning, with unknown duration
but will inevitably reoccur sometime. With the help of control
cards it becomes possible to track down the cause of the unnatural
variability. The effectiveness and permanence of the correction
can be proven using control cards.
Figure 236: SPC and quality assurance systems