# PDCA

**URL:** https://kaizumi.com/dictionary/pdca

**Description:** PDCA (Plan-Do-Check-Act) is a four-step continuous improvement cycle for testing changes and learning from results.

**Category:** lean-tools

**Tags:** problem-solving, foundational

## 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. Deming later refined the cycle into PDSA, replacing "Check" with "Study" to stress learning over inspection.

## Examples

### Manufacturing

> 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).

### Healthcare

> A clinic hypothesized that phone reminders would reduce no-shows (Plan). They tested with one provider's patients for a month (Do). They compared no-show rate to previous months and control group (Check). Results showed 30% reduction, so they expanded to all providers (Act).

### Administrative

> A team hypothesized that a new template would speed invoice processing (Plan). They piloted with two processors for two weeks (Do). They measured processing time and error rate (Check). Results showed faster processing but more errors; they modified the template and cycled again.

## 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.

## Play It

Run the cycle yourself: **A3 Investigator** has you investigate a factory crisis the PDCA way — grasp the situation, find the root cause, test a countermeasure, and confirm the result.

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Source: https://kaizumi.com/dictionary/pdca
Licence: free to quote and cite with attribution to Kaizumi.