PDCA cycle
PDCA cycle (Plan-Do-Check-Act) is an iterative four-step management method for continuous improvement of processes and products, also known as the Deming Cycle or Deming Wheel, providing a systematic framework for implementing and evaluating changes (Deming W.E. 1986, p.88)[1]. The factory floor has a defect problem. Someone proposes a solution. Do they just implement it and hope for the best? The PDCA approach is more disciplined: Plan the change carefully. Do it on a small scale. Check whether it worked. Act on what you learned—either adopt, adapt, or abandon. Then cycle again.
Walter Shewhart developed the original concept at Bell Laboratories in the 1930s as part of statistical process control. W. Edwards Deming refined and popularized it in Japan during the 1950s, where it became foundational to the Japanese quality revolution. The Japanese Union of Scientists and Engineers formalized the PDCA terminology in 1951. Deming himself preferred PDSA (Plan-Do-Study-Act), believing "study" better captured the analytical intent than "check." Either way, the core idea endures: improvement requires systematic experimentation, not just good intentions.
The four stages
Each step serves a specific purpose:
Plan
Define the problem. What exactly needs improvement? Gather data to understand current state[2].
Analyze root causes. Why does the problem exist? Use tools like fishbone diagrams and the 5 Whys.
Develop hypothesis. What change might produce improvement? Predict expected results.
Create action plan. Specify what will be done, by whom, when, and how success will be measured.
Do
Implement on small scale. Test the change in a controlled, limited way[3].
Document everything. Record what actually happens—expected and unexpected.
Collect data. Measure the outcomes specified in the plan.
Check
Analyze results. Did the change produce the expected improvement? Compare actual to predicted outcomes[4].
Identify learnings. What worked? What didn't? What surprised you?
Assess viability. Is the change worth implementing broadly?
Act
Standardize success. If the change worked, implement it fully. Create new standard procedures[5].
Address problems. If results were poor, analyze why and plan the next cycle.
Restart the cycle. Continuous improvement means the cycle never truly ends.
Applications
PDCA applies across domains:
Quality management
Process improvement. Reducing defects, variation, and waste. Foundation of Six Sigma and Lean methodologies.
Problem solving. Structured approach to persistent quality issues[6].
Healthcare
Clinical improvements. Reducing medication errors, improving patient outcomes.
Administrative efficiency. Streamlining scheduling, reducing wait times.
Project management
Risk management. Testing approaches before full commitment.
Iterative development. Agile methods echo PDCA principles.
Benefits
The cycle offers advantages:
Systematic rigor. Prevents jumping to solutions without proper analysis[7].
Learning orientation. Each cycle generates knowledge regardless of outcome.
Risk reduction. Small-scale testing before full implementation.
Employee engagement. Involves workers in improvement, fostering ownership and accountability.
Common pitfalls
Organizations stumble when:
Skipping Plan. Rushing to action without adequate analysis of root causes.
Weak Check. Failing to rigorously assess whether changes actually worked[8].
One-and-done. Treating PDCA as a single event rather than ongoing cycle.
Scope too large. Trying to change too much at once, making learning impossible.
| PDCA cycle — recommended articles |
| Quality management — Continuous improvement — Six Sigma — Lean manufacturing |
References
- Deming W.E. (1986), Out of the Crisis, MIT Press.
- Shewhart W.A. (1939), Statistical Method from the Viewpoint of Quality Control, Dover.
- Moen R.D., Norman C.L. (2010), Circling Back, Quality Progress, 43(11).
- ASQ (2024), PDCA Cycle.
Footnotes
- ↑ Deming W.E. (1986), Out of the Crisis, p.88
- ↑ Shewhart W.A. (1939), Statistical Method, pp.34-48
- ↑ Moen R.D., Norman C.L. (2010), Circling Back, pp.22-28
- ↑ ASQ (2024), PDCA Cycle
- ↑ Deming W.E. (1986), Out of the Crisis, pp.112-128
- ↑ Shewhart W.A. (1939), Statistical Method, pp.89-104
- ↑ Moen R.D., Norman C.L. (2010), Circling Back, pp.28-32
- ↑ ASQ (2024), PDCA Cycle
Author: Sławomir Wawak