What is a Plan-Do-Check-Act (PDCA)?
PDCA — the Shewhart/Deming cycle — is the engine of continuous improvement: Plan a change with a predicted outcome, Do it small, Check results against the prediction, Act by standardizing what worked or discarding what didn't. Then spin again.
The step organizations skip is Check — changes get rolled out, never measured, and improvement becomes churn. The prediction made in Plan is what gives Check its teeth.
Worked example
A precast plant predicts that pre-staging rebar cages will cut cycle time per element by 15% (Plan). One production line tries it for three weeks (Do). Actual gain: 11%, plus an unexpected crane-congestion cost (Check). The practice rolls out with a revised staging layout that fixes the crane issue (Act) — and the next cycle targets the curing schedule. Improvement as a loop, not a memo.