Control Charts Do Not Control Processes--People Do


Propst, Annabeth L.   (1991, ASQC)   Process Management International, Rockford, IL

Annual Quality Congress, Milwaukee WI    Vol. 45    No. 0
QICID: 9741    May 1991    pp. 784-787
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Article Abstract

This paper shows how companies can use control charts to achieve the objective of continuous improvement by involving the employees in every aspect of control charting and empowering employees to implement needed changes in their processes.

As companies strive for continuous improvement, control charts can: (1) help detect the presence of special causes so that action can be taken, (2) guard against losses due to tampering and minimize the effects of the two kinds of errors associated with control charts, (3) help assess when the process is stable so the chart may be used for predictive purposes; and (4) monitor the behavior of the process over time.

Each time a special cause is identified, it is necessary to determine ways to prevent its recurrence or to minimize the effects of the recurrence; this strategy produces a more efficient process with less variation and higher productivity. Once special causes are eliminated, control charts can be used to predict the average delivery time, the probability of producing parts within the specification limits, the variation between the biggest part and the smallest part, etc. Finally, the control chart can monitor changes to a process and indicate when it is necessary to take action.


Control charts,Special causes,Statistics,Continuous improvement (CI)

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