Quality Control

Photo: W. J. Latzko, Ph.D.
W. J. Latzko, Ph.D.
Walter A. Shewhart, the originator of modern methods for quality, wrote, “For our present purpose a phenomenon will be said to be controlled when, through the use of past experience, we can predict, at least within limits, how the phenomenon may be expected to vary in the future.” (Shewhart, 1931, p. 6)

His definition of “control” was that if a phenomenon, such as the error rate in a call center, was consistent within the upper and lower control limit, it was in control. As long as the process remained unchanged, the phenomenon would continue to generate the same range of errors in the future as it has in the past. If the range of errors is too high for management to tolerate, they, management, must change the process. The workers cannot do any better than the process lets them. To exhort workers to improve without giving the a way of doing this is futile. As Myron Tribus stated in his paper, “Managing to Survive in a Competitive world” (Tribus, 1992, p. 30),”The workers work in the system, the managers should work on the system to improve it with their help.”

Many people think of quality control as an inspection system of output. Workers think of quality control as big brother watching and pouncing if a mistake is detected. Unfortunately these conditions exist and are extremely counterproductive. True quality control looks at the process and determines whether the process is still operating as intended or not. If it has drifted (as evidenced by a special cause of variation) it needs to be brought back into the predictable limits.

One can work with a predictable system to improve it. Improvement efforts on an unpredictable or chaotic system may solve one problem but cause a host of others. Usually, such efforts cause more grief than they solve.

It is unfortunate that the image of quality control degenerated into a perceived police action and so lost its original meaning of cost effective predictable process. One can only hope that as a profession, we re-discover the benefits of true quality control.

Reference List

Shewhart, W. A. (1931). Economic control of quality of manufactured product. Princeton, NJ: D. Van Nostrand Company.

Tribus, M. (1992). Quality First: Selected Papers on Quality & Productivity Improvement. (Fourth ed.) Alexandria, VA: National Institute for Engineering Management and Systems.