PDCA is an iterative four-step management method used in business for the control and
continuous improvement of processes and products. It is also known as the Deming circlewheel,
Shewhart cycle, control circle/cycle, or plan–do–study–act. Another version of this PDCA cycle is OPDCA.
The added "O" stands for observation or as some versions say "Grasp the current condition."
This emphasis on observation and current condition has currency with Lean manufacturing/Toyota
Production System literature.
Meaning
The steps in each successive PDCA cycle are: PLAN
Establish the objectives and processes necessary to deliver results in accordance with the
expected output. By establishing output expectations, the completeness and accuracy of the spec
is also a part of the targeted improvement. When possible start on a small scale to test
possible effects. DO
Implement the plan, execute the process, make the product. Collect data for charting and
analysis in the following "CHECK" and "ACT" steps.
CHECK Study the actual results and compare against
the expected results to ascertain any differences. Look for deviation in implementation from
the plan and also look for the appropriateness and completeness of the plan to enable the
execution, i.e., "Do". Charting data can make this much easier to see trends over several
PDCA cycles and in order to convert the collected data into information. Information is what
you need for the next step "ACT". ACT
Request corrective actions on significant differences between actual and planned results.
Analyze the differences to determine their root causes. Determine where to apply changes
that will include improvement of the process or product. When a pass through these four
steps does not result in the need to improve, the scope to which PDCA is applied may be
refined to plan and improve with more detail in the next iteration of the cycle, or attention
needs to be placed in a different stage of the process.
Note: Some modern trainers now also refer to the "A" as "Adjust". This helps trainees
to understand that the 4th step is more about adjusting/correcting the difference between
the current state and the planned state instead of thinking that the "A" is all about action
and implementation stage).
About PDCA was made popular by Dr W. Edwards Deming,
who is considered by many to be the father of modern quality control; however, he always
referred to it as the "Shewhart cycle". Later in Deming's career, he modified PDCA to "Plan,
Do, Study, Act" because he felt that "check" emphasized inspection over analysis.
The concept of PDCA is based on the scientific method, as developed from the work of Francis
Bacon. The scientific method can be written as "hypothesis"–"experiment"–"evaluation"
or plan, do and check. Shewhart described manufacture under "control"—under statistical
control—as a three-step process of specification, production, and inspection. He also specifically
related this to the scientific method of hypothesis, experiment, and evaluation. Shewhart says
that the statistician "must help to change the demand [for goods] by showing [...] how
to close up the tolerance range and to improve the quality of goods." Clearly, Shewhart intended
the analyst to take action based on the conclusions of the evaluation. According to Deming, during
his lectures in Japan in the early 1950s, the Japanese participants shortened the steps
to the now traditional plan, do, check, act. Deming preferred plan, do, study, act because
"study" has connotations in English closer to Shewhart's intent than "check".
A fundamental principle of the scientific method and PDCA is iteration—once a hypothesis
is confirmed, executing the cycle again will extend the knowledge further. Repeating the
PDCA cycle can bring us closer to the goal, usually a perfect operation and output.
Another fundamental function of PDCA is the "hygienic" separation of each phase, for if
not properly separated measurements of effects due to various simultaneous actions risk becoming
confounded. PDCA is also known as a system for developing
critical thinking. At Toyota this is also known as "Building people before building
cars." Toyota and other Lean companies propose that an engaged, problem-solving workforce
using PDCA is better able to innovate and stay ahead of the competition through rigorous
problem solving and the subsequent innovations. This also creates a culture of problem solvers
using PDCA and creating a culture of critical thinkers.
In Six Sigma programs, the PDCA cycle is called "define, measure, analyze, improve, control".
The iterative nature of the cycle must be explicitly added to the DMAIC procedure.
Deming continually emphasized iterating towards an improved system, hence PDCA should be repeatedly
implemented in spirals of increasing knowledge of the system that converge on the ultimate
goal, each cycle closer than the previous. One can envision an open coil spring, with
each loop being one cycle of the scientific method - PDCA, and each complete cycle indicating
an increase in our knowledge of the system under study. This approach is based on the
belief that our knowledge and skills are limited, but improving. Especially at the start of
a project, key information may not be known; the PDCA—scientific method—provides feedback
to justify our guesses and increase our knowledge. Rather than enter "analysis paralysis" to
get it perfect the first time, it is better to be approximately right than exactly wrong.
With the improved knowledge, we may choose to refine or alter the goal. Certainly, the
PDCA approach can bring us closer to whatever goal we choose.
Rate of change, that is, rate of improvement, is a key competitive factor in today's world.
PDCA allows for major "jumps" in performance, as well as Kaizen. In the United States a
PDCA approach is usually associated with a sizable project involving numerous people's
time, and thus managers want to see large "breakthrough" improvements to justify the
effort expended. However, the scientific method and PDCA apply to all sorts of projects and
improvement activities. See also
AIDA process Business process improvement
COBIT DMAIC
Lesson study OODA loop
Performance management Quality management
Quality storyboard Robert S. Kaplan
Theory of Constraints Total Security Management
Six sigma Lean
References
Further reading Shewhart, Walter Andrew. Economic Control
of Quality of Manufactured Product/50th Anniversary Commemorative Issue. American Society for
Quality. ISBN 0-87389-076-0. The Improvement Guide: A Practical Approach
to Enhancing Organizational Performance, 2nd Edition by Gerald J. Langley, Ronald Moen,
Kevin M. Nolan, Thomas W. Nolan, Clifford L. Norman, Lloyd P. Provost Published by Jossey-Bass
ISBN 978-0-470-19241-2 Shewhart, Walter Andrew. Statistical Method
from the Viewpoint of Quality Control. New York: Dover. ISBN 0-486-65232-7.
Deming, W. Edwards. Out of the Crisis. MIT Center for Advanced Engineering Study. ISBN 0-911379-01-0.
External links PDCA Guidance