Plan-do-check-act is the Deming (or, more correctly, Shewhart) learning cycle:


You have an idea for improvement. Plan for a test of the idea. Don’t just try it, plan how you will know if you are right or wrong (plans should include measurement).


Carry out your test.

Check (or study)

Study the results. What have you learned?



• adopt the change
• abandon it
• try it again
• change it and try it again (i.e. go to plan)

Starting at ‘plan’ is just fine if you are already a systems thinker. If you are not, you will be at risk of failing to understand your real problem. That’s why the Vanguard Method starts at ‘check’ or ‘study’, not ‘plan’.

It is also worth pointing out that ‘Act’ in PDCA means ‘put it in the line’. Deming was an advocate of testing ideas off-line in manufacturing.