Design Thinking & Innovation
5 Whys Analysis
Find the cause behind the symptom by asking "why" until the answer points at something you can change.
- Time: 10 to 20 min
- With: Alone or with the people closest to the problem
- You get: A cause chain and one concrete countermeasure
How to use this worksheet
- Describe the problem as a fact: what happened, where, when, how big. No blame, no guess about the cause.
- Answer the first "why" with something you can check. Each answer must explain the one above it.
- Keep going until the answer is a process, rule or missing safeguard you can change. Five is a rule of thumb: stop earlier or go further.
- Read the chain backwards ("therefore"). If a step does not follow, it is a guess: go back and verify.
- Write one countermeasure per root cause, with an owner and a date.
What exactly went wrong? Stick to observable facts.
Prompts and example
Ask yourself
- What did you observe, and who noticed?
- When and where did it start and end?
- How big was the impact (customers, money, time)?
Example
The website was unavailable for 2 hours on Tuesday between 14:10 and 16:05. About 1,800 checkout attempts failed.
The direct, immediate cause.
Prompts and example
Ask yourself
- Can you point to evidence (log line, metric, witness)?
Example
The application server ran out of memory and restarted repeatedly.
Explain the answer above, not the original problem.
Prompts and example
Example
The new image-resize code released that morning never freed its buffers.
Look for the gap that let the previous cause through.
Prompts and example
Example
The feature was only tested with small sample images.
Now you are usually at process level: rules, checks, ownership.
Prompts and example
Example
Our release checklist has no load or soak test step.
If this answer is a person ("Alex forgot"), keep asking: what made forgetting possible?
Prompts and example
Example
Nobody owns the release checklist, so it has not been updated since the team doubled.
Name the cause you will address and what changes, who does it and by when.
Prompts and example
Ask yourself
- If this were fixed, would the original problem have been prevented?
- Is there a cheaper fix further up the chain?
- How will you know it worked?
Example
Root cause: no owner for the release checklist. Countermeasure: appoint a checklist owner; add a 15-minute soak test with production-sized data. Owner / date: Dana, in place by 30 November.
Before you finish
- Every answer is backed by evidence, not by opinion.
- Reading the chain from the bottom up, each step is a plausible reason for the one above.
- The root cause is something your team can change, not a person's character.
- Complex failures often have several causes: if the chain forks, run a second chain for the other branch.
About the 5 Whys
The 5 Whys technique was developed by Sakichi Toyoda and became a core practice of the Toyota Production System. The idea is simple: repeatedly asking why moves you from the symptom to a cause you can actually act on.
It works best for problems with a fairly linear cause. For tangled problems with many contributing factors, combine it with a fishbone diagram so you do not mistake the first plausible chain for the whole story.
Recommended reading
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- The Toyota WayJeffrey K. Liker
Comprehensive guide to Toyota's management principles including the 5 Whys technique developed by Sakichi Toyoda.
- The Lean StartupEric Ries
Modern application of Toyota principles including root cause analysis for startup problem-solving.