Five Whys: root cause analysis
Root cause analysis: find the underlying cause of a problem by asking 'why?' five times in pairs. A Toyota technique.
Time
10–15 min
Form
In pairs
Phase
Deepen · Close
Materials
Not needed
Step-by-step instructions
4 steps · 10–15 min
- Form the pairs
Sit in pairs, one sheet per pair — you are writing a chain, and it has to be readable back in one go. - Why 1
Show the problem. Ask “why does this happen?” and write the pair's answer down. - Why 2 to 5
Ask why again — of your own PREVIOUS answer this time, not of the problem. Each answer goes under the last. The final answer is usually the cause. - Compare with the class
One sentence per pair: which cause ended up at the bottom? Close with the question of which cause is within their own reach.
Worth knowing
Five is the name of the structure, not a law of nature: three works in a short lesson, seven for a stubborn problem. You set it in the preparation.
Step 3 is where it goes wrong. A pair that asks why five times about the original problem ends up with five symptoms side by side instead of one chain. Walk past and check that it is written one under the other — then it is going well.
The gain is in step 4, not at the fifth why. Two pairs starting from the same problem and arriving at different causes: that is the conversation.
Tips for the facilitator
Separating cause from effect
Five whys deep — past the symptom
Reflection on something that went wrong
The group drops its quick conclusions
- One or more concrete problems — set these in the settings, each on a new line. Phrase them as an observable situation ("The assignment is handed in late"), not as a judgement.
- Time per "why" — set this in the settings (default 90 seconds per round, discussed together in pairs).
- A way to record the five answers: on paper, on the board, or digitally. Writing them down makes the chain of causes visible.
- Shorter or longer: stop before five times if the root cause is already clear, or keep going if there is another layer underneath.
- With debrief: have pairs compare their root cause. Different pairs often arrive at a different point — showing that one problem can have several causes.
- Branching: sometimes one "why" has two answers. Let the pair choose which trail to follow, or briefly explore both.
- Appreciative: apply the same question to something that went well ("why did this work?") to uncover success factors.
- Mentoring / reflection: why work keeps being handed in late, why collaboration runs stiffly.
- History: tracing the causes behind an event step by step.
- Citizenship / social studies: reading a social issue back to its underlying cause.
- Physics / chemistry: why an experiment turned out differently than expected.
- Economics: why a company or decision did not produce the intended result.
This activity is based on the "five whys" method by Sakichi Toyoda, developed within the Toyota Production System to address the root cause of breakdowns rather than the symptoms. It develops analytical and causal thinking: the distinction between what you see happening and why it happens.
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