mingyao743/make-rational-decision/pdca-cycle

PDCA Cycle (Plan-Do-Check-Act)

A four-step iterative management method for continuous improvement of processes, products, and workflows.

When to Use

• Process improvement initiatives
• Quality management and lean operations
• Iterative product development
• Change management rollouts
• Any workflow that needs ongoing refinement

The Four Phases

         ┌──────────┐
         │  PLAN    │
         │          │
         │ Set goals │
         │ Design    │
         │ the plan  │
         └────┬─────┘
              │
              ▼
         ┌──────────┐
         │   DO     │
         │          │
         │ Execute   │
         │ the plan  │
         │ (small    │
         │  scale)   │
         └────┬─────┘
              │
              ▼
         ┌──────────┐
         │  CHECK   │
         │          │
         │ Measure   │
         │ results   │
         │ vs goals  │
         └────┬─────┘
              │
              ▼
         ┌──────────┐
         │   ACT     │
         │          │
         │ Standardize│
         │ success or │
         │ correct &  │
         │ restart    │
         └────┬─────┘
              │
              └──────▶ (next cycle)

Phase Details

P — Plan

Define the objective, identify the gap, and design a plan to close it.

• Identify the problem or opportunity: What needs improvement?
• Set measurable goals: What does success look like? (Use SMART criteria)
• Analyze root causes: Why does the current gap exist? (Use fishbone or 5-Whys)
• Design the intervention: What change will we test?
• Define metrics: How will we measure the outcome?
• Plan the execution: Who, when, where, how?

Output: A documented plan with goals, actions, metrics, and timeline.

D — Do

Execute the plan, ideally on a small scale first.

• Implement the change: Execute according to the plan
• Monitor execution: Track deviations from the plan
• Collect data: Record quantitative and qualitative observations
• Document issues: Note any problems encountered during execution

Output: Execution results, raw data, and observation notes.

C — Check

Compare actual results against planned goals.

• Analyze the data: Did the metrics improve as expected?
• Compare to baseline: What changed vs. the starting state?
• Identify gaps: Where did results fall short of expectations?
• Surface unexpected outcomes: What side effects appeared?
• Assess statistical significance: Is the improvement real or noise?

Output: A results assessment with quantitative comparison and qualitative findings.

A — Act

Standardize successes or adjust and restart the cycle.

• If goals were met:
• Standardize the new process (update documentation, train teams)
• Communicate the improvement to stakeholders
• Identify the next area for improvement (start a new PDCA cycle)
• If goals were partially met:
• Identify what worked and what didn't
• Adjust the plan based on learnings
• Restart the PDCA cycle with refined approach
• If goals were not met:
• Analyze why the intervention failed
• Return to Plan phase with new understanding

Output: Standardized procedures, lessons learned, and the next cycle's plan.

Output Format

## PDCA Cycle: [Improvement Topic]
 
### Cycle: #[N] — [Date Range]
 
#### P — Plan
- **Problem**: [What needs improvement]
- **Goal**: [SMART goal]
- **Root cause**: [Why the gap exists]
- **Intervention**: [What change to test]
- **Metrics**: [What to measure]
- **Baseline**: [Current metric values]
 
#### D — Do
- **Actions taken**: [What was executed]
- **Execution period**: [Dates]
- **Deviations**: [What differed from plan]
- **Observations**: [Qualitative notes]
 
#### C — Check
| Metric | Baseline | Target | Actual | Status |
|--------|----------|--------|--------|--------|
| [Metric 1] | [Value] | [Value] | [Value] | ✅/❌ |
| [Metric 2] | [Value] | [Value] | [Value] | ✅/❌ |
 
- **Unexpected outcomes**: [Side effects, surprises]
- **Key learnings**: [Insights gained]
 
#### A — Act
- **Decision**: [Standardize / Adjust / Abandon]
- **Standardization**: [New process documentation, if applicable]
- **Next cycle focus**: [What to improve next]

Extensions

This skill is enhanced by the following shared extensions:

• `_shared/diagram-renderer.md` — Mermaid flowchart template for rendering the PDCA cycle with decision branching
• `_shared/tracking-system.md` — Essential for PDCA; provides file-based persistence for cycle records, baselines, and cumulative improvement tracking
• `_shared/skill-workflows.md` — Workflows 1, 4, 5, and 6 all use PDCA as the final execution + verification step
• `_shared/examples-library.md` — Example 8 shows a complete PDCA cycle with metrics tracking

Rules

• Start small — test changes on a limited scale before full rollout
• Each cycle must have clearly defined, measurable goals (never "improve quality" — use "reduce defect rate from 5% to 2%")
• The Check phase must use real data, not subjective impressions
• Never skip the Act phase — without standardization, improvements are lost
• PDCA is cyclical, not linear — the end of one cycle feeds the beginning of the next
• Document every cycle, even failed ones — learning from failure is a core outcome