Using this data, the operator can detect when a process is not meeting the requirements of the bell curve percentages. Thus, the potential problems are eliminated before scrap is created. For example, a home owner will eliminate a fire hazard, such as a frayed electrical cord, before the house catches on fire. The control charts are numbered and the control limits are labeled. The charts then are given to the person responsible for the process for data collection.
Control limits can change.
As the process becomes more accurate, the control limits will become closer together.