CirckBgancil
Clearing up
myths about theDeming cycle
and seeing how it
keeps evolving

In 50 Words
Or Less• In the 1950s, W. Edwards
Deming brought thescientific method to industry. Later, the method
was called the plan-dostudy-act (PDSA) cycle.
• Deming built the methodfrom many problem-solving theories, including
Shewhart’s specification,production and inspection process.
• PDSA remains one oftoday’s most popular
problem-solving methods
and continues to evolve.

by Ronald D. Moen
and Clifford L. Normanbasic quality

THERE STILL SEEMS to be much confusion surrounding
W. Edwards Deming’s plan-do-study-act (PDSA) cycle. The misunderstandings
can be summarized by three basic questions:
1. How did Deming’s PDSA cycle evolve?
2. Did Deming create the plan-do-check-act (PDCA) cycle?
3. Are PDCA and PDSA related?
Before answering these questions and clearing up the misconceptions, it’s
important to review the PDSA cycle’s foundation, which starts with the scientific method.

November 2010  •  QP 23

Figure 1 shows the evolution of the scientific meth-John Dewey became a leading proponent of prag-od and the PDSA cycle, starting with Galileo Galilei inmatism, and his works influenced philosophy, educa-1610, pragmatism in the early 1900s and the evolutiontion, religion, government and democracy around theof the PDCA and PDSA cycles through 1993.

world.2 James and Dewey’s pragmatism could be summarized in one statement: People are the agents ofThe foundation

their own destinies.

Galileo, considered by many to be the father ofClarence I. Lewis, an American pragmatist also

modern science, made original contributions toeducated at Harvard, was heavily influenced by Peirce

the science of motion and strengths of materials byand James. Lewis set out three ideas in Mind and thecombining designed experiments and mathematics.

World Order to further the pragmatists’ influence:3

Through his studies, conducting designed experi-

1. A priori truth is definitive and offers criteria throughments became the cornerstone of science and thescientific method.

which experience can be discriminated.
2. The application of concepts to any particular expe-

Sir Francis Bacon made his contribution to modern
science as a philosopher who was concerned about

rience is hypothetical, and the choice of conceptual
system meets pragmatic needs.

how knowledge is developed. He believed knowledge

3. The susceptibility of experience to conceptual in-generation must follow a planned structure. At theterpretation requires no particular metaphysical as-time, science depended on deductive logic to interpret

sumption about the conformity of experience to thenature.

mind or its categories.

Bacon insisted that scientists should instead proceed through inductive reasoning—from observations

Shewhart and Demingto axiom to law. His contribution completed the inter-

Lewis’ book had enormous influence on Walter A.

play between deductive and inductive logic that under-

Shewhart and Deming in bringing the scientific methodlies how we advance knowledge.

to 20th century industry.

Charles Peirce and William James were students at

Shewhart’s Statistical Method From the Viewpoint

Harvard University in Cambridge, MA, in January 1872of Quality Control, published in 1939, first introduced

when they formed a discussion group called the Meta-

the concept of a straight-line, three-step scientific pro-physical Club.1 This group would forever be linked

cess of specification, production and inspection.4 Hewith the uniquely American philosophy called pragma-

later revised this idea into a cyclical concept. Figure 2tism. The group said the function of thought is to guidecontrasts the two views of Shewhart’s idea of specifica-

action and that truth is preeminently to be tested bytion, production and inspection.

the practical consequences of belief.

“These three steps must go in a circle instead of in

Evolution of the scientific method and PDSA cycle   /   Figure 1
Father of modernscience
Galileo (1610)

PragmatismCharles PeirceWilliamJames (1872)

Inductive learning
Francis Bacon(1620)

How We ThinkJohn Dewey(1933)

PDCA = plan-do-check-act
PDSA = plan-do-study-act

Integration ofpragmatismand empiricism
C.I. Lewis (1929)

TQC = total quality control
QC = quality control

24 QP  •  www.qualityprogress.com

Shewhart cycle
WalterShewhart (1939)

Deming wheel
W. Edwards
Deming (1950)

Shewhart cycle
Deming (1986)

PDCA
Japanese QC(1951)

PDCA
Kaoru Ishikawa
TQC (1985)

PDSA
Deming (1993)

basic quality

Shewhart cycle—1939   /   Figure 2

Deming wheel—1950   /   Figure 3

Shewhart straight-line process
Step one

Step two

Step three

Specification

Production

Inspection

Shewhart cyclical concept

ecification
Sp4132

1. Design the product (with appropriate tests).

Product

3. Sell the product.
4. Test the product in service and through market
research. Find out what users think about it and why
nonusers have not bought it.

nion
ctiope2. Make the product and test in the production line andin the laboratory.

Insa straight line, as shown,” Shewhart wrote. “It may beseminars into the PDCA cycle.7 Table 1 shows Imai’shelpful to think of the three steps in the mass production

description of the relationship between the Deming

process as steps in the scientific method. In this sense,wheel and the PDCA cycle.

specification, production and inspection correspond re-

Imai did not provide details about which execu-

spectively to hypothesizing, carrying out an experimenttives reworked the wheel or how they translated theand testing the hypothesis. The three steps constitute

Deming wheel into the PDCA cycle. No one has evera dynamic scientific process of acquiring knowledge.”5claimed ownership of this revision or disputed Imai’s

Shewhart’s concept eventually evolved into whatbecame known as the Shewhart cycle.
Deming had a front-row seat for Shewhart’s think-assertion.
The resulting PDCA cycle, shown in Figure 4 (p.
26), shows the four-step cycle for problem solving. Theing: At the age of 39, Deming edited a series of lec-cycle includes:

tures Shewhart delivered to the U.S. Department of

1. Plan: Define a problem and hypothesize possible

Agriculture into what eventually became the basis ofShewhart’s 1939 book.
Deming built off Shewhart’s cycle and modified thecauses and solutions.
2. Do: Implement a solution.
3. Check: Evaluate the results.

concept. He got the chance to present the new versionof the cycle in 1950 during an eight-day seminar in Japan sponsored by the Japanese Union of Scientists andEngineers (JUSE).6
In his new version of the cycle, Deming stressed

The Deming wheel vs. theJapanese PDCA cycle   /   Table 1

the importance of constant interaction among the four
steps of design, production, sales and research. He em-1. Design = plan

Product design corresponds to the planning phase ofmanagement.

2. Production = do

Production corresponds to doing. making or working on
the product that was designed.

3. Sales = check

Sales figures confirm whether the customer is satisfied.

4. Research = act

If a complaint is filed, it must be incorporated into theplanning phase and action taken in the next round ofefforts

phasized that these steps should be rotated constantly,
with quality of product and service as the aim, as shownin Figure 3. This new version is referred to as the Deming wheel, the Deming cycle or the Deming circle.

Deming wheel evolves
According to Masaaki Imai, Japanese executives recast the Deming wheel presented in the 1950 JUSEPDCA = plan-do-check-act

November 2010  •  QP 25

4. Act: Return to the plan step if the results are unsatisfactory, or standardize the solution if the results
are satisfactory.

Japanese PDCAcycle—1951   /   Figure 4

The PDCA cycle also emphasized the prevention oferror recurrence by establishing standards and the on-ActPlanCheckDogoing modification of those standards.
Once again, others wanted to enhance and revise

PDCA = plan-do-check-act

the cycle. This time, it was Kaoru Ishikawa. He redefined the PDCA cycle to include more in the planning
step: determining goals and targets, and formulating
methods to reach those goals.8 Figure 5 shows thePDCA cycle and incorporates Ishikawa’s changes.
In the do step, Ishikawa also included training andPDSA cycle evolution

education to go along with implementation. Ishikawa

More than 30 years after Deming first revised thesaid good control meant allowing standards to be re-Shewhart cycle, Deming again reintroduced it during

vised constantly to reflect the voices of consumers andfour-day seminars he hosted in the 1980s.10 He said thetheir complaints, as well as the requirements of the next

latest version had come directly from the 1950 version.

process. The concept behind the term “control” (kanri)would be deployed throughout the organization.

“Any step may need the guidance of statisticalmethodology for economy, speed and protection fromThe PDCA cycle, with Ishikawa’s updates andfaulty conclusions from failure to test and measure theimprovements, can be traced back to S. Mizuno

effects of interactions,” Deming said.11 Figure 6 illus-of the Tokyo Institute of Technology in 1959. Thetrates the procedure to follow for improvement.

seven basic tools (check sheet, histograms, Pareto

Deming warned his audiences that the PDCA ver-chart, fishbone diagram, graphs, scatter diagramssion is frequently inaccurate because the English wordand stratification) highlight the central principle of“check” means “to hold back.”

Japanese quality. These tools—together with theOnce again, Deming modified the Shewhart cycle in

PDCA cycle and the quality control (QC) story for-1993 and called it the Shewhart Cycle for Learning and9improvement

Improvement—the PDSA cycle, as shown in Figure 7.12(kaizen) in Japan and are still being used today.

Deming described it as a flow diagram for learning andmat—became

thefoundationforimprovement of a product or a process.

Japanese PDCA cycle—1985   /   Figure 5

PDCA vs. PDSAOver the years, Deming had strong beliefs about thePDCA cycle and clearly wanted to distinguish it fromTake
appropriateaction.

Check theeffects ofimplementation.

Determinegoals andtargets.
Determine
methods ofreaching goals.
Engage ineducation andtraining.

the PDSA cycle.
At a roundtable discussion on product quality atthe U.S. Government Accounting Office, Deming wasasked how the QC circle (referring to PDCA) and theDeming circle related.
“They bear no relation to each other,” Deming said.
“The Deming circle is a quality control program. It isa plan for management. Four steps: Design it, makeit, sell it, then test it in service. Repeat the four steps,over and over, redesign it, make it, etc. Maybe you

Implement
work.

could say that the Deming circle is for management,
and the QC circle is for a group of people that workon faults encountered at the local level.”13

PDCA = plan-do-check-act

26 QP  •  www.qualityprogress.com

On Nov. 17, 1990, Deming wrote a letter to Ronald

basic quality

D. Moen to comment on the manuscript for Improving Quality Through Planned Experimentation,
coauthored by Moen, Thomas R. Nolan and Lloyd P.

Shewhart cycle:
Deming—1986  /   Figure 6

Provost.14 “Be sure to call it PDSA, not the corruption
PDCA,” Deming wrote in the letter.15
In response to a letter he received in 1991, Demingcommented about a chart labeled plan-do-check-act.
“What you propose is not the Deming cycle,” he wrote
in the letter. “I don’t know the source of the cycle thatyou propose. How the PDCA ever came into existence

Study the results.
What did we learn?
What can we predict?

I know not.”16

Has the Deming PDSA cycle evolved?

Observe the effectsof the change or test.

StepfourWhat could be the team’s mostimportant accomplishments?
What changes might bedesirable? What data are available?
Are new observations needed?
Step If yes, plan a change or test.
Decide how to use theone
observations.

Step Step
three twoIn 1991, Moen, Nolan and Provost added to Deming’sPDSA planning step of the improvement cycle and required the use of prediction and associated theory.17

Carry out the change ortest decided upon,preferably on a small scale.

Step five. Repeat step one, with knowledge accumulated.
Step six. Repeat step two, and onward.

The authors said the study step compared the observed data to the prediction as a basis for learning.
This provided the deductive-inductive interplay necessary for learning as required in the scientific method.
It is not enough to determine that a change resulted
in improvement during a particular test, according toMoen, Nolan and Provost. As you build your knowl-

PDSA cycle: Deming—1993   /   Figure 7
Act—Adopt the change,abandon it or run throughAthe cycle again.

Plan—Plan a changeor test aimed at
P improvement.

edge, you will need to be able to predict whether achange will result in improvement under the different
conditions you will face in the future.
Three years later, Gerald Langley, Kevin Nolan andStudy—Examine theSresults. What did welearn? What went wrong?

DDo—Carry outthe change or test
(preferably on a small scale).

PDSA cycle and Model for
Improvement—1991, 1994   /   Figure 8ActPlan• What changes • Objective.
• Questions
are to beand predictions.
made?
• Plan to carry out• Next cycle?
the cycle (who,what, where, when).
StudyDo• Complete the • Carry out the plan.
data analysis. • Document problems
and unexpected• Compare data
observations.
to predictions.
• Begin data
• Summarize
analysis.
what waslearned.

Model for Improvement
What are we trying
to accomplish?
How will we know that achange is an improvement?
What change can we make thatwill result in improvement?

ActPlanStudyDoNovember 2010  •  QP 27

basic quality

Deming had strong beliefs about thePDCA cycle and wanted to distinguishit from the PDSA cycle.
Thomas Nolan added three basic questions to supplement the PDSA cycle. Figure 8 (p. 27) shows the de18

tailed cycle and the Model for Improvement.
This new approach provides a basic framework fordeveloping, testing and implementing changes to theway things are done that will lead to improvement.19-20
The approach supports a full range of improvement efforts from the very informal to the most complex—forexample, the introduction of a new product line or service for a major organization.

Continuing evolution
As Imai pointed out, Japanese executives recast theDeming wheel and developed the PDCA cycle, building from Deming’s JUSE seminars of 1950. PDCA has
not changed drastically in the last 40 years. It is clear,
however, that Deming never fully embraced the PDCA
cycle. PDCA and PDSA seem related only through thescientific method.
From 1986 to 1993, Deming was committed to evolving his PDSA cycle, and he always referred to it as theShewhart cycle for learning and improvement. It’s usedfor learning, testing and implementation.
Today, the PDSA cycle remains relevant and continues to evolve. QP

2.	Larry A. Hickman and Thomas M. Alexander, eds., The Essential Dewey, Vol.
1, Pragmatism, Education, Democracy, Indiana University Press, 1998.
3.	Clarence I. Lewis, Mind and the World Order, reprinted by Dover Press,1929.
4. Walter A. Shewhart, Statistical Method From the Viewpoint of Quality Control, U.S. Department of Agriculture, reprinted by Dover, 1939, p. 45.
5.	Ibid.
6. W. Edwards Deming, Elementary Principles of the Statistical Control of Quality, Japanese Union of Scientists and Engineers, 1950.
7. Masaaki Imai, Kaizen: The Key to Japan’s Competitive Success, Random
House, 1986, p. 60.
8. Kaoru Ishikawa, What is Total Quality Control? The Japanese Way, PrenticeHall, 1985, pp. 56-61.
9. Paul Lillrank and Noriaki Kano, Continuous Improvement: Quality Control
Circles in Japanese Industry, Center for Japanese Studies, University ofMichigan, 1989, pp. 23-25.
10. Ronald D. Moen and Clifford L. Norman, “The History of the PDCA Cycle,”
proceedings from the Seventh Asian Network for Quality Congress, Tokyo,
Sept. 17, 2009.
11. W. Edwards Deming, Out of the Crisis, Massachusetts Institute of Technology Press, 1986, p. 88.
12. W. Edwards Deming, The New Economics, Massachusetts Institute ofTechnology Press, 1993, p. 35.
13. Proceedings from the U.S. Government Accounting Office’s Roundtable
Discussion Product Quality—Japan vs. United States, 1980, p. 76, http://archive.gao.gov/d46t13/087733.pdf.
14. Ronald D. Moen, Thomas R. Nolan and Lloyd P. Provost, Improving Quality
Through Planned Experimentation, McGraw-Hill, 1991, p. 11.
15. W. Edwards Deming, personal letter to Ronald D. Moen, Nov. 17, 1990.
16. Peter B. Peterson, “Library of Congress Archives: Additional Information
About W. Edwards Deming (1900-1993),” Journal of Management History,Vol. 3, No. 2, 1997, pp. 98-119.
17. Moen, Nolan and Provost, Improving Quality Through Planned Experimentation, see reference 14.
18. Gerald Langley, Kevin Nolan and Thomas R. Nolan, “The Foundation ofImprovement,” Quality Progress, June 1994, p. 81.
19. Gerald Langley, Kevin Nolan, Thomas R. Nolan, Clifford L. Norman and Lloyd
P. Provost, The Improvement Guide, Jossey-Bass, 1996, p. 10.
20. Gerald Langley, Kevin Nolan, Thomas R. Nolan, Clifford L. Norman andLloyd P. Provost, The Improvement Guide, second edition, Jossey-Bass,2009, p. 24.

Editor’s Note:
One of the authors, Ronald D. Moen, had the unique opportunity to workwith W. Edwards Deming. From 1982-1986, Moen managed Deming’s
monthly visits to General Motors’ Pontiac Motor Division. At the time, Moen
worked as director of statistical methods. From 1982-1993, Moen assisted
Deming at 70 of his well-known four-day seminars. During that time, Deming
also reviewed several papers and a book Moen co-authored. Moen andClifford L. Norman gave a presentation on the history of PDCA at the Asian
Network for Quality Conference last year in Tokyo. Some of the content of
this article was adapted from that presentation.

RONALD D. MOEN is a partner at Associates inProcess Improvement in Georgetown, TX. He has amaster’s degree in statistics from the University ofMissouri in Columbia. He is a member of ASQ andreceived ASQ’s Deming Medal in 2002.

ACKNOWLEDGEMENT
The authors thank their colleagues at Associates in Process Improvement—Tom Nolan, Kevin Nolan, Jerry Langley and Lloyd Provost—who offered guidance and worked on the Model for Improvement.

REFERENCES
1.	Louis Menand, The Metaphysical Club—A Story of Ideas in America, Farrar,Straus and Giroux, 2001.

28 QP  •  www.qualityprogress.com

CLIFFORD L. NORMAN is a partner at Associates inProcess Improvement. He has a master’s degree inbehavioral science from California State University atDominquez Hills. He is a senior member of ASQ.