The 5 Whys
Ask 'why' five times to reach the root cause.
Explanation
Toyota developed this technique to find root causes without jumping to conclusions. Each 'why' peels back a layer, revealing the real problem. Most people stop at symptoms (why #1 or #2) and miss the actual cause (why #4 or #5).
Real-World Example
Amazon's website crashed: Why? Database overloaded. Why? Too many product searches. Why? New recommendation algorithm queries 10x more. Why? No performance testing before deploy. Why? Deadline pressure skipped QA. ROOT CAUSE: Broken deployment process. FIX: Mandatory load testing. Another: Customers complaining about app. Why? It's slow. Why? Images take forever to load. Why? They're 5MB each. Why? Designer exports at print quality. Why? Nobody specified mobile requirements. ROOT: No design guidelines.
How to Apply
Rules: Write each answer down (memory fails). Stick to facts, not guesses. Focus on process, not people. Stop when you reach: company policy, human nature, or external factors you can't control. The final answer should prevent recurrence, not just fix this instance. If multiple paths emerge, follow each.