Control limits

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”).

Use

Control limits are used to detect signals in process data that indicate that a process is not in control and therefore not operating predictably. A signal is defined as any single point outside of the control limits. A process is also considered out of control if there are seven consecutive points, still inside the control limits but on one single side of the mean.

For normally distributed statistics, the area bracketed by the control limits will on average contain 99.73% of all the plot points on the chart, as long as the process is and remains in statistical control. A false-detection rate of at least 0.27% is therefore expected.

See also

• Acceptable quality limit

References

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This industry-related article is a stub. You can help Wikipedia by expanding it.v · Categories: Statistical terminology Statistical charts and diagrams Management Quality Quality control Evaluation methods Process management Project management Statistics stubs Industry stubs Wikimedia Foundation. 2010. Игры ⚽ Поможем сделать НИР USS Hampden County (LST-803) Freud the Secret Passion Look at other dictionaries: control limits — The upper and lower limits on the acceptable level of cash that minimizes the sum of the opportunity cost ( opportunity costs) of excessive cash and the cost of marketable security transactions. Bloomberg Financial Dictionary …   Financial and business terms Control chart — One of the Seven Basic Tools of Quality First described by Walter A. Shewhart …   Wikipedia Control (management) — Controlling is one of the managerial functions like planning, organizing, staffing and directing. It is an important function because it helps to check the errors and to take the corrective action so that deviation from standards are minimized… …   Wikipedia Control of Asbestos Regulations 2006 — The Control of Asbestos Regulations 2006 came into force in the United Kingdom on 13 November 2006 and brought together a number of other asbestos related pieces of legislation.[1] The pieces of legislation the regulations revoked and replaced… …   Wikipedia Control-Feedback-Abort Loop — Too often systems fail, sometimes leading to significant loss of life, fortunes and confidence in the provider of a product or service. It was determined that a simple and useful tool was needed to help in the analysis of interactions of groups… …   Wikipedia Control of Vibration at Work Regulations 2005 — The Control of Vibration at Work Regulations 2005 are set of regulations created under the Health and Safety at Work etc. Act 1974 which came into force in Great Britain on 6 July 2005.[1] The Regulations place a duty on employers to reduce the… …   Wikipedia control chart — A graphical representation of the statistically derived performance limits (normally ±2 standard deviations), which is used in statistical process control By recording samples on a control chart, it is possible to identify the trends and to take… …   Big dictionary of business and management control — con|trol1 W1S1 [kənˈtrəul US ˈtroul] n ▬▬▬▬▬▬▬ 1¦(make somebody/something do what you want)¦ 2¦(power)¦ 3¦(way of limiting something)¦ 4¦(ability to stay calm)¦ 5¦(machine/vehicle)¦ 6¦(people who organize activity)¦ 7¦(scientific test)¦… …   Dictionary of contemporary English control — con|trol1 [ kən troul ] noun *** ▸ 1 power to make decisions ▸ 2 power over machine etc. ▸ 3 law limiting something ▸ 4 ability to stop problem ▸ 5 ability to remain calm ▸ 6 switch on machine ▸ 7 in scientific test ▸ 8 check rules are applied ▸… …   Usage of the words and phrases in modern English control */*/*/ — I UK [kənˈtrəʊl] / US [kənˈtroʊl] noun Word forms control : singular control plural controls Get it right: control: The noun control is sometimes followed by of and sometimes by over. The choice of preposition depends on the verb that comes… …   English dictionary 18+ © Academic, 2000-2024 Contact us: Technical Support, Advertising Dictionaries export, created on PHP, Joomla, Drupal, WordPress, MODx. Mark and share Search through all dictionaries Translate… Search Internet Share the article and excerpts Direct link … Do a right-click on the link above and select “Copy Link”