Introduction to Control Charts

摘要

Control charts, also known as Shewhart charts or process-behavior charts, are graphs tracking how a process changes over time. When applied to process control they are used to determine whether a manufacturing or business process is in a state of control, i.e. the range of variation within a process after special causes have been eliminated. A process under control (i.e. stable, has variation due only to sources common to the process), so data from the process can be used to predict how the process will perform in the future. If the chart indicates that the process is not in control, analysis of the chart can help determine the causes of variation, which should then be removed to bring the process back into control. A control chart allows special causes of variation to be differentiated from natural variability of the process.