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Guided walkthrough that asks one why at a time, requires evidence at every step, flags blame language, and produces a printable summary with a system corrective action. Built the way Toyota actually uses it, not the way it is taught in slide decks.
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FAQ
No. Five is a guide, not a rule. Stop when you reach a system cause you can actually change. Sometimes that is at three whys, sometimes at seven. The trap is stopping early at the operator. The other trap is asking why so many times you end up at “human nature” or “the universe,” which is not actionable. Stop at the first cause that is a process, standard, equipment, or system you can fix.
That is the most common 5 Why failure mode. Toyota practice is respect for people, which means we do not blame them for system failures. When the answer is “the operator forgot” or “did not follow the procedure,” the next why is “why was the procedure unclear, why was the visual standard not in place, why was the supervisor not present, why was the station not error-proofed.” Push past the person to the system that allowed the person to fail.
Because 5 Why done in a conference room produces a fix for the wrong problem. The Toyota practice is genchi genbutsu: go and see for yourself. Every why in the chain should be verified at the line by direct observation, talking to the operator, or pulling the data. If you have not gone and seen, you are guessing.
Twenty to sixty minutes if you are doing it correctly. Most of that time is the go-and-see verification at each step, not the writing. If you finished in under ten minutes, you almost certainly skipped verification. Walk back to the line with the operator and check each why before you commit to a corrective action.
Use 5 Why when the problem has one obvious chain of cause. Use a fishbone when there are multiple potential causes to visualize. Use a full RCA when the problem is high-severity, recurring, or customer-facing and you need containment plus corrective plus preventive action documented.
BUILT BY OPERATORS, NOT CONSULTANTS