Definition
The 5 Whys is a structured questioning technique that repeatedly asks "why" a problem occurred, each answer forming the basis for the next question, typically five times, until the chain reaches a root cause that can actually be corrected rather than a superficial symptom.
Key facts
- A simple, structured chain of "why" questions, each building directly on the previous answer.
- "Five" is a guideline, not a fixed rule: the chain continues until a genuinely actionable root cause is reached, which may take more or fewer steps.
- Works best for straightforward, single-path problems; complex failures with multiple contributing branches often need a fault tree instead.
- Depends on each "why" answer being evidence-based, not assumed; otherwise the chain can drift toward a plausible-sounding but incorrect cause.
What does 5 Whys reveal about failures?
The 5 Whys starts from a clearly stated problem and asks why it happened; the answer becomes the next question's starting point, repeating until the chain reaches a cause the team can act on directly (a specific missing step, a worn part, an undocumented procedure) rather than a vague or unfalsifiable explanation.
How do teams use 5 Whys in failure analysis?
Root cause analysis (RCA) is the broader discipline of finding evidence-based root causes, of which the 5 Whys is one simple technique suited to linear problems. Fault Tree Analysis instead maps multiple possible contributing branches and their logical combinations, better suited when several factors could combine to cause the same failure.
FAQ
Frequently asked questions
How does repeated "why" questioning help structured root-cause clarification?
The 5 Whys chains repeated "why" questions, each answer feeding the next question, tracing a superficial symptom back to a specific, actionable root cause, typically in about five steps for straightforward, single-path problems.
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