Process Control Charts

The process control chart is a tool used to record and display data on the operation of a process over time in a way that is simple to use and interpret.

It is used to assist in:

• bringing the process under control by displaying the variation within the process
• identifying problems or potential difficulties by distinguishing between special and common causes of variation
• keeping the process under continual control by drawing attention to situations which either require immediate action to remove special causes, thus returning the process to a stable condition, or require management action to reduce the level of common cause variation in order to increase quality and contribute to continual improvement

Thus control charts, which were developed by the American statistician Dr. Shewhart in the 1920's, present a picture of what is happening in a process.