five-whys-root-cause

Five Whys Root Cause

Use this skill to run Five Whys Root Cause as a practical consulting method, not as a generic framework explanation.

Method Notes

• Ask why until reaching a controllable cause, not a person to blame.
• Branch when the answer has multiple causes.

Required Inputs

Collect or infer these inputs before execution:

• problem statement
• evidence
• timeline
• constraints and failed fixes

If an input is missing, do not block automatically. Mark it as missing, state the assumption used, and add a validation action.

When Not To Use

Do not use when the problem has several interacting causal paths, feedback loops, or insufficient event evidence. A single Why chain can oversimplify a multi-causal system.

Adjacent Methods

• fishbone-diagram: use when several cause branches must be compared.
• systems-thinking: use when feedback, delay, or incentives keep recreating the issue.
• constraint-analysis: use when one limiting factor is already visible.

Step-by-Step Execution

Step	Required input	How to execute	Output
State problem	Observed issue, impact, scope, time.	Write one clear problem without blame.	Problem statement.
Ask first why	Problem and immediate evidence.	Explain the direct cause with evidence.	Cause 1.
Continue why chain	Previous cause and evidence.	Ask why again until reaching a controllable system/process cause.	Cause chain.
Branch if needed	Cause chain with multiple plausible causes.	Split into parallel why chains when one answer hides multiple causes.	Cause branches.
Convert to prevention	Root cause and constraints.	Define corrective action, owner, deadline, and recurrence check.	Root-cause action plan.

Output Template

### 1. Problem Statement
Observed problem:
Expected state:
Evidence:
Boundary:

### 2. Why Chain
| Level | Why did this occur? | Evidence | Assumption |
|---|---|---|---|
|  |  |  |  |

### 3. Root Cause Judgment
Candidate root cause:
Mechanism:
Inside control:
Alternative branch:

### 4. Corrective And Preventive Action
| Action | Owner | Timing | Recurrence signal | Validation |
|---|---|---|---|---|
|  |  |  |  |  |

### Evidence And Next Decision
- Confirmed facts:
- Assumptions:
- Missing evidence:
- Next action, owner, and timing:
- Expected signal and decision threshold: