Skill542 repo starsupdated 2d ago

nw-five-whys-methodology

The nw-five-whys-methodology implements Toyota's Five Whys root cause analysis with structured multi-causal branching to investigate complex problems across five progressive levels from symptoms to fundamental causes. Use this skill when analyzing failures, defects, or system issues that require comprehensive investigation beyond surface symptoms, ensuring all contributing factors are identified, validated through evidence, and addressed with preventive solutions.

View source Repository: nWave

Install in Claude Code

Copy

git clone --depth 1 https://github.com/nWave-ai/nWave /tmp/nw-five-whys-methodology && cp -r /tmp/nw-five-whys-methodology/nWave/skills/nw-five-whys-methodology ~/.claude/skills/nw-five-whys-methodology

Then start a new Claude Code session; the skill loads automatically.

Definition

SKILL.md

# Five Whys Methodology

## Philosophical Foundation

Taiichi Ohno: "By repeating why five times, the nature of the problem as well as its solution becomes clear."

Core tenets: scientific evidence-based investigation | address fundamental causes not symptoms | solve to prevent recurrence | use findings for Kaizen

## Multi-Causal Investigation

Complex problems have multiple root causes. Investigate comprehensively:
- **Parallel**: investigate all symptoms/conditions simultaneously
- **Branch**: follow each cause through all five WHY levels
- **Cross-cause**: ensure multiple causes don't contradict
- **Comprehensive**: address all root causes, not just primary

## WHY Level Definitions

### WHY 1: Symptom Investigation
What is immediately observable? Investigate all symptoms. Each branch continues independently. Document verifiable evidence per symptom.

```
WHY 1A: Path not found [Evidence: file exists but wrong context -- Windows vs WSL paths]
WHY 1B: Permission denied [Evidence: user context mismatch between host and container]
WHY 1C: Timing issues [Evidence: race conditions with file system operations]
```

### WHY 2: Context Analysis
Why does this condition exist? Follow each WHY 1 through context. Check if factors connect multiple causes. Examine system/environment/operational context.

### WHY 3: System Analysis
Why do conditions persist? How system enables multiple failure modes. How causes interact systemically. Analyze design/architecture decisions.

### WHY 4: Design Analysis
Why not anticipated? Review design assumptions. Identify all design blind spots. Trace decisions to original context.

### WHY 5: Root Cause Identification
Fundamental causes. Multiple root causes expected for complex issues. Ensure all contributing causes identified. Focus on deepest level.

## Validation and Verification

### Evidence Requirements
Each WHY level must have verifiable evidence for all causes. Root causes must explain all symptoms collectively. Solutions must address all root causes.

### Backwards Chain Validation
1. Trace each root cause forward to symptom | 2. "If this exists, would it produce this symptom?" = must be yes
3. Cross-validate: multiple roots must not contradict | 4. Completeness: "Missing contributing factors?" at each level

### Solution Completeness
Every root cause -> corresponding solution | Prevent recurrence, not just mitigate | Use findings for system improvement

## Branch Documentation Format

```
PROBLEM: [clear problem statement]

WHY 1A: [symptom] [Evidence: ...]
  WHY 2A: [context] [Evidence: ...]
    WHY 3A: [system factor] [Evidence: ...]
      WHY 4A: [design factor] [Evidence: ...]
        WHY 5A: [root cause] [Evidence: ...]
        -> ROOT CAUSE A: [fundamental cause]
        -> SOLUTION A: [prevention strategy]

WHY 1B: [symptom] [Evidence: ...]
  WHY 2B: [context] [Evidence: ...]
    ...

CROSS-VALIDATION:
- Root Cause A + Root Cause B: [consistent/contradictory]
- All symptoms explained: [yes/no, gaps if any]
```