5 Whys

Toyota's root-cause drill on one page, drawn as a descending ladder. State the problem, then ask "why?" five times in a row — each answer becomes the thing the next "why" asks about — until the chain lands on a cause you can actually fix. The first answer is nearly always a symptom: the release slipped because QA found bugs, the bugs shipped because tests were skipped, tests were skipped to hit a deadline, and so on down to something structural you can change. Five rungs hang on a single spine so the whole causal chain reads as one descent, ending in a root-cause bar and the countermeasure that addresses it — not the symptom up top. Five is a guide, not a rule: stop when you hit an actionable cause, and if the chain forks, run a fresh sheet down each branch. Fill it in to work a problem through, or print it blank and drill down by hand.

• Portrait
• 1 page
• Reflection

Best for: Getting past the obvious symptom to the structural cause of a recurring problem — so the fix actually sticks.