Western Electric rules

Western Electric rules

In Statistical Process Control, the Western Electric Rules are decision rules for detecting "out-of-control" or non-random conditions on control charts.Citation
last = Montgomery
first = Douglas C.
publication-date = 2005
title = Introduction to Statistical Quality Control
edition = 5
publication-place = Hoboken, New Jersey
publisher = John Wiley & Sons
isbn = 9780471656319
oclc = 56729567 Locations of the observations relative to the control chart control limits (typically at ±3 standard deviations) and centerline indicate whether the process in question should be investigated for assignable causes. The Western Electric Rules were codified by a specially-appointed committee of the manufacturing division of the Western Electric Company and appeared in the first edition of its Statistical Quality Control Handbook in 1956.Citation
last = Western Electric Company
publication-date = 1956
title = Statistical Quality Control handbook.
edition = 1
publication-place = Indianapolis, Indiana
publisher = Western Electric Co.
oclc = 33858387
page = v Their purpose was to ensure that line workers and engineers interpret control charts in a uniform way.Citation
last = Western Electric Company
publication-date = 1956
title = Statistical Quality Control handbook.
edition = 1
publication-place = Indianapolis, Indiana
publisher = Western Electric Co.
oclc = 33858387
page = 25

Motivation

The rules attempt to distinguish unnatural patterns from natural patterns based on several criteria:Citation
last = Western Electric Company
publication-date = 1956
title = Statistical Quality Control handbook.
edition = 1
publication-place = Indianapolis, Indiana
publisher = Western Electric Co.
oclc = 33858387
page = 24
#The absence of points near the centerline (identified as a mixture pattern)
#The absence of points near the control limits (identified as a stratification pattern)
#The presence of points outside the control limits (identified as an instability pattern)
#Other unnatural patterns (systematic (autocorrelative), repetition, trend patterns)

To achieve this, the rules divide the chart into zones, measured in units of standard deviation (σ) between the centerline and control limits, as follows:

For other control charts based on skewed distributions, the Handbook recommends:
#Finding the probabilities associated with each zone
#Devising tests that should result in the desired sensitivity to the presence of assignable causes

Other unnatural patterns

The Handbook also identifies patterns that require consideration of both the upper and lower halves of the control chart together for identification:

ee also

*Nelson rules

References


Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать курсовую

Look at other dictionaries:

  • Nelson rules — are a method in process control of determining if some measured variable is out of control (unpredictable versus consistent). Rules, for detecting out of control or non random conditions were first postulated by Walter A. Shewhart [1] in the… …   Wikipedia

  • Western Australia — Western Australian. a state in W Australia. 1,273,624; 975,920 sq. mi. (2,527,635 sq. km). Cap.: Perth. * * * State (pop., 2001: 1,906,114), western Australia. Covering 976,790 sq mi (2,529,880 sq km), it constitutes one third of the continent s… …   Universalium

  • Western culture — For this article s equivalent regarding the East, see Eastern culture. For the Henry Cow album of the same name, see Western Culture (album). Leonardo da Vinci s Vitruvian Man. A symbol of the importance of humanism and empiricism in Western… …   Wikipedia

  • theatre, Western — ▪ art Introduction       history of the Western theatre from its origins in pre Classical antiquity to the present.       For a discussion of drama as a literary form, see dramatic literature and the articles on individual national literatures.… …   Universalium

  • New Rules for Boats — Origin Perth, Australia Genres Indie pop Years active 2004–present Labels QStik Records/MGM Distribution …   Wikipedia

  • dance, Western — Introduction       history of Western dance from ancient times to the present and including the development of ballet, the waltz, and various types of modern dance.       The peoples of the West of Europe and of the countries founded through… …   Universalium

  • History of Western Subcultures in the 20th Century — 1900 World War IIn the early part of the 20th century, subcultures were mostly informal groupings of like minded individuals. The Bloomsbury group in London was one example, providing a place where the diverse talents of people like Virginia… …   Wikipedia

  • Great Western Railway — The Great Western Railway (GWR) was a British railway company and a notable example of civil engineering, linking London with the West Country, South West England and South Wales. It was founded in 1833, kept its identity through the 1923… …   Wikipedia

  • colonialism, Western — ▪ politics Introduction       a political economic phenomenon whereby various European nations explored, conquered, settled, and exploited large areas of the world.       The age of modern colonialism began about 1500, following the European… …   Universalium

  • Metrorail Western Cape — Region A Metrorail train pulling out of Kalk Bay station. Info …   Wikipedia

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”