Plan Do Check Act – it didn’t come from Deming


Plan-Do-Check-Act Deming circle, also known as...

Plan-Do-Check-Act Deming circle, also known as the Shewart cycle, since Deming claimed he took the idea from him. Later Deming changed it to be Plan-Do-Study-Act, but the first version seems more popular and has become the defacto standard. (Photo credit: Wikipedia)

Walter A. Shewhart

Walter A. Shewhart (Photo credit: Wikipedia)

We’ve all seen PDCA – the famous process control cycle. While delivering a Product Owner Class at our offices in New Jersey, the home of Bell Labs, I learned something I didn’t know about PDCA. One of my colleagues pointed out that W. Edwards Deming was NOT the inventor of it! I had been attributing PDCA to Deming. It is often referred to as the Deming Cycle or Deming Circle. The person who came up with PDCA was Walter A. Shewhart. Dr. Shewhart worked at Bell Labs! I’ve always been impressed with the innovation at Bell Labs, so learning about the origin of PDCA was particularly satisfying.

Shewhart was also credited with the statistical control chart and the distinction between assignable-cause and chance-cause variance. These ideas go to the heart of LEAN manufacturing, and ultimately, Agile development. For example, the notion of work loading assumes that chance-cause variance is not removable, and as a result, we engineer throughput to take chance-cause into account, and simultaneously use PDCA to remove assignable-cause variance. And we focus on adjusting the process to remove assignable cause variance.

PDCA is sometimes misapplied. We plan a whole release,, we do a whole release, we check a whole release, and then we attempt to improve the whole release. Instead, applying PDCA on increments of a release brings us closer to the ideal of continuous improvement. Shewhart introduced this idea during the development of telephone transmission systems.

Is Shewhart the real father of LEAN?