What is the 5 Whys analysis?
Quick answer
Why-why analysis, better known as the 5 Whys, is a simple problem-solving method: you ask “why?” repeatedly, usually about five times, until you get past the symptoms to the root cause of a problem. It was developed at Toyota by founder Sakichi Toyoda and popularized by Taiichi Ohno as part of the Toyota Production System.
How to run a 5 Whys
- Define the problemWrite one clear, specific problem statement, such as ‘Customer orders shipped late this week.’
- Ask whyAsk why it happened and write down the answer, based on facts rather than guesses.
- RepeatAsk why about that answer. Keep going until you reach a cause you can fix, often around the fifth why.
- Fix the root causeAgree on an action that addresses the root cause, not just the symptom.
- Check it workedFollow up later to confirm the problem doesn’t come back.
A classic example
Problem: The car won’t start.
| Why? | Answer |
|---|---|
| 1. Why won’t the car start? | The battery is dead. |
| 2. Why is the battery dead? | The alternator isn’t working. |
| 3. Why isn’t the alternator working? | Its belt has broken. |
| 4. Why did the belt break? | It was past its service life and never replaced. |
| 5. Why wasn’t it replaced? | The car wasn’t serviced on schedule. |
Root cause: No maintenance schedule. Replacing the battery would only fix the symptom; following a service schedule prevents it happening again.
Where it’s used
The 5 Whys started in manufacturing but is now common in software teams (incident reviews), healthcare (patient safety), customer service and even personal problem-solving. It’s often combined with other tools such as the fishbone (Ishikawa) diagram.
Common mistakes
- Stopping too early at a symptom.
- Blaming people (“Bob forgot”) instead of asking why the system allowed it.
- Guessing instead of checking facts.
- Following only one path when a problem has several causes; you can branch into more than one chain.
- Treating “five” as a strict rule; sometimes three whys are enough, sometimes you need seven.
Why it works
It’s fast, needs no special software and gets teams talking about processes rather than blame. For a bigger-picture way of using “why,” see Simon Sinek’s Start With Why. Troubleshooting a device? The same thinking helps with problems like a slow computer.
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