PDCA (Plan, Do, Check, Act) is the improvement cycle popularised by W. Edwards Deming. It's the mental model behind almost every Lean and quality practice.
The four phases
- Plan: form a hypothesis. What change will you try, and what result do you expect?
- Do: run the experiment. Small-scale, controlled, brief.
- Check: measure the actual result against the expected. Did it work?
- Act: if it worked, standardise. If it didn't, learn from it and go back to Plan.
Why cycles matter
PDCA is deliberately a loop, not a project. Real improvement is dozens of small cycles, each teaching you something. The organisations best at continuous improvement don't run big transformations - they run PDCA cycles constantly at every level.