Statistical Process Control (SPC) is used for quality control to ensure that the process produces within customer requirements.

With SPC you can detect errors early and prevent problems, rather than correct problems as they occur.

SPC also helps you to respond properly to measurement result and to address stability and capability.

I once had a summer job at “Sjømennenes Helsehjem”, and how to boil the eggs was a hot topic.

The residents were not always pleased with the boiled eggs. However, it was complicated to please them since some residents were very happy while others were dissatisfied, with eggs cooked exactly the same way.

"The devil is in the details"

Improving quality is about understanding and controlling variation.

Several variables influence a result. However, some variables are more important than others.

All measurements involve uncertainty.

Suppliers of measuring equipment usually specify the measurement uncertainty as a symmetrical interval around the measurement result:

Measurement result ± measurement uncertainty

Example: The length of a special measuring rod is 2000 mm ± 1 mm.

Variation can be positive in contexts like "varied workday," "varied training", etc.

For manufacturing companies variation can create headaches and huge cost.

When and how do you respond to a result?

Do you use facts or intuition? Do your customers decide when to react?

Or maybe you use statistical process control?

How do you react? Do you start looking for a special cause?