Western Electric Rules

Western Electric Rules refer to a set of criteria for statistical quality control that were identified by a committee of the manufacturing division of the Western Electric Company and published in the first edition of its Statistical Quality Control Handbook in 1956. These rules were proposed to enhance the sensitivity of basic control charts in detecting shifts in process parameters and are sometimes used in the form of runs-rules.From: Fundamentals of Industrial Quality Control [2018], Adjusting external calibration intervals for auxiliary devices in testing laboratories according to intermediate checks results [2021], Double exponentially weighted moving average control chart with supplementary runs-rules [2020]

Control Charts

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Purchase Book

Published in Lawrence S. Aft, Fundamentals of Industrial Quality Control, 2018

Lawrence S. Aft

Although a single point outside of the control limits immediately signals an out of control process, there are some other indications that are commonly used to identify assignable or abnormal variation. Duncan presents five additional criteria for identifying out of control processes (Duncan, 1974, p. 392). There are many other criteria that can be used as well. Sometimes these criteria are referred to as “Western Electric Rules”. This is based on guidelines suggested in the original Western Electric Quality Control Handbook. One or more points in the vicinity of the two sigma warning limits.A run of seven or more points. (The run may be seven consecutive ascending points, seven consecutive decreasing points, or seven points above or below the mean.)Cyclical patterns of points.A run of three points outside the two sigma limits.A run of five points outside the one sigma limits.

Adjusting external calibration intervals for auxiliary devices in testing laboratories according to intermediate checks results

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Journal Information

Published in Water Science, 2021

Seleem E. Gaber

Western Electric Rules (WECO rules) are decision rules for detecting “out-of-control” or nonrandom conditions on control charts. The Western Electric Rules were identified by a specially appointed committee of the manufacturing division of the Western Electric Company and published in the first edition of its Statistical Quality Control Handbook in 1956 (Western Electric Company, 1956).

Western Electric Rules

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Control Charts

Adjusting external calibration intervals for auxiliary devices in testing laboratories according to intermediate checks results