noun

• A chart designed to help monitor or analyse a particular process; especially one that allows the spread of data to be analysed by means of a line representing the mean and two further lines at a distance of three standard deviations from the mean.

  One of the commonest and earliest forms of control chart was invented in 1926 by Walter A. Shewhart (1891–1967) as a means of quickly identifying outliers which may arise during quality control.