In the 1930s, the U.S. physicist Walter Andrew Shewhart subjected the production process at a Western Electric plant to a systemic review. The focus was on continuous quality improvement. Four steps have been established to ensure learning success. Plan: The person responsible must identify potential for improvement. Do: The optimization concept is tested. Check: The implemented concept is evaluated. Act: If the result is positive, implementation takes place on a broad front (e.g. in other plants) and the effect is checked regularly.