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Performance Management Best Practice

Statistical Process Control for Quality Improvement

by Priscilla Wisner

Table of contents

Executive Summary

  • Statistical process control (SPC) is a management philosophy that relies on straightforward statistical tools to identify and solve process problems.

  • By systematically identifying potential problems in process control, managers can proactively make corrections before quality outcomes suffer.

  • SPC methods are useful in helping managers to measure whether their processes and products conform to design specifications, and they also help organizations to improve productivity and reduce waste.

  • SPC methods are used extensively in manufacturing settings but are also relevant in the service sector.


Statistical process control (SPC) is an optimization philosophy centered on using a variety of statistical tools to enable continuous process improvement. Closely linked to the total quality management (TQM) philosophy, SPC helps firms to improve profitability by improving process and product quality. Although initially used in manufacturing, SPC tools and methods work equally well in a service environment.

SPC methods are used extensively by organizations to enable systematic learning. Using methods developed in the 1920s by Walter Shewhart and subsequently enhanced by quality consultants William Edwards Deming and Joseph Juran, organizations are able to use a set of straightforward statistics to find out whether or not their processes conform to expectations. Furthermore, the use of SPC methods can help to identify instances of process variation that may signal a problem in the process. By identifying process variation and potential nonconformance with design expectations early in the production or service environment, managers can proactively make corrections before the process variation negatively impacts quality and customer perceptions.

An Overview

Although SPC is enabled with statistical analysis, the management philosophy that underlies SPC is much broader than a set of statistics. To improve a process systematically, managers must first identify key processes and key variables of interest. Every organization has hundreds, if not thousands, of processes and variables that can affect product and service outcomes, and one challenge is to focus on the processes and variables that are of key concern. SPC tools can be useful in identifying areas that need attention, but managerial insight is needed to use the SPC tools strategically.

Managers can directly influence organizational performance using SPC practices. Their choice of key processes and performance variables creates a feed-forward signaling device to the organization about key performance indicators. This causes attention to be paid to these processes and variables. Feedback is then received through the SPC information, enabling evaluation of the data and an opportunity for corrective actions to be taken. Thus, SPC is not merely a set of statistical tools, but a management philosophy that helps organizations to improve performance through feed-forward and feed-back loops.

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Further reading


  • Amsden, Robert T., Howard E. Butler, and Davida M. Amsden. SPC Simplified: Practical Steps to Quality. 2nd ed. New York: Productivity Press, 1998.
  • Crossley, Mark. L. The Desk Reference of Statistical Quality Methods. 2nd ed. Milwaukee, WI: ASQ Quality Press, 2007.
  • Pyzdek, Thomas. The Six Sigma Handbook: The Complete Guide for Green Belts, Black Belts, and Managers at All Levels. New York: McGraw-Hill, 2003.


  • American Society for Quality (ASQ), a professional association dedicated to learning about quality and the improvement of quality in organizations. ASQ administers the prestigious Malcolm Baldrige National Quality Award. Membership is available to individuals or organizations:
  • iSixSigma, an online forum and extensive statistical process control resources:
  • Management and Accounting Web (MAAW), dedicated to education, research, and the practice of management and accounting disciplines. Contains links to dozens of management and finance resources:
  • Managers-Net, an archive of articles and examples of management topics. Click on “Contents” and then on “Index to the complete Technical Archive” for an alphabetical list of topics:
  • Quality America, Inc., has resources for implementing SPC tools, including articles, an encyclopedia, technical references, and interpretation guides for SPC analysis:

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