Control limits, also known as natural process limits, are horizontal lines drawn on a statistical process control chart, usually at a distance of ±3 standard deviations of the plotted statistic from the statistic's mean.
Control limits should not be confused with tolerance limits or specifications, which are completely independent of the distribution of the plotted sample statistic. Control limits describe what a process is capable of producing (sometimes referred to as the “voice of the process”), while tolerances and specifications describe how the product should perform to meet the customer's expectations (referred to as the “voice of the customer”).
Read more about Control Limits: Use
Famous quotes containing the words control and/or limits:
“The human mind is indeed a cave swarming with strange forms of life, most of them unconscious and unilluminated. Unless we can understand something as to how the motives that issue from this obscurity are generated, we can hardly hope to foresee or control them.”
—Charles Horton Cooley (1864–1929)
“Predatory capitalism created a complex industrial system and an advanced technology; it permitted a considerable extension of democratic practice and fostered certain liberal values, but within limits that are now being pressed and must be overcome. It is not a fit system for the mid- twentieth century.”
—Noam Chomsky (b. 1928)