PDCA
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PDCA (Plan-Do-Check-Act) is a four-step continuous improvement cycle for testing changes and learning from results.
Definition
PDCA (Plan-Do-Check-Act), also known as the Deming Cycle or Shewhart Cycle, is a four-step iterative method for continuous improvement. Plan: develop a hypothesis and plan an experiment. Do: execute the plan on a small scale. Check: analyze results against expectations. Act: adopt the change if successful, abandon if not, or modify and cycle again. PDCA provides a structured approach to testing changes, learning from results, and building knowledge systematically rather than making changes based on untested assumptions.
Examples
A team hypothesized that changing cutting fluid would reduce tool wear (Plan). They tested the new fluid on one machine for a week (Do). They measured tool life and compared to baseline (Check). Results showed 20% improvement, so they implemented across all machines (Act).
Key Points
- PDCA is a learning cycle—each iteration builds knowledge
- Small-scale experiments reduce risk of large-scale failures
- "Check" compares results to predictions, not just final outcomes
- The cycle repeats—there's no final state, only continuous improvement
Common Misconceptions
PDCA is just project management. PDCA is scientific method applied to improvement—hypothesis testing, not just task execution. The "Check" phase analyzes whether the hypothesis was correct, not just whether tasks were completed.
One PDCA cycle solves the problem. Complex problems require multiple cycles. Initial experiments reveal what works; subsequent cycles refine and expand. Expecting one cycle to solve everything defeats the purpose.