5 Whys

The 5 Whys is a root cause analysis technique developed by Sakichi Toyoda and used within the Toyota Production System. It's deceptively simple: when a problem occurs, you ask "Why?" five times to drill down from symptoms to the underlying root cause. The power lies in its simplicity — no complex tools or statistical analysis required.

1. State the problem clearly — Write down the specific problem you're experiencing. Be precise and factual.
2. Ask "Why?" the first time — Why did this problem happen? Write down the answer.
3. Ask "Why?" again — Take your first answer and ask why that happened. Write it down.
4. Repeat until you reach the root cause — Continue asking "Why?" for each answer. Five is a rule of thumb — you might need fewer or more iterations.
5. Identify the root cause — You'll know you've reached it when the answer points to a process, policy, or systemic issue rather than a person or one-off event.
6. Define a countermeasure — Address the root cause with a corrective action that prevents recurrence.

• Stay focused on one causal chain at a time
• Avoid jumping to conclusions
• Base answers on facts, not assumptions
• If you branch into multiple causes, follow each branch separately

1. Why? The server ran out of memory.
2. Why? Traffic was 10x higher than the server could handle.
3. Why? We didn't do capacity planning for the launch.
4. Why? There's no checklist or process for launch preparation.
5. Why? We've never formalized our launch process — each team handles it ad hoc.

The 5 Whys helps you stop treating symptoms and start fixing root causes. It's quick, requires no special tools, and works for problems of any size — from production incidents to team process issues.