Five Whys

A root-cause analysis technique, associated with Toyota engineer Taiichi Ohno, that repeatedly asks "why" to move from a surface symptom to a deeper underlying cause. Referenced here as a real precedent for the disciplined, evidence-based habit the judgment portfolio builds; the full technique is taught in Module 3. (see Topic 3.3)

A root cause analysis technique originating in the Toyota Production System, in which an investigator repeatedly asks "why" to trace a symptom back to a deeper cause. Useful for going deeper on a single line of causation; not, by itself, a method for discovering that multiple independent contributing factors exist.

The habit, from Toyota's production system, of asking "why" of each answer in turn until you reach a condition you can actually change rather than a description of the output. The number is not sacred; the discipline of not stopping early is.

A root-cause technique that asks "why?" repeatedly, each answer feeding the next, to drill from a surface symptom down to a systemic process cause; foundational to the Toyota Production System under Taiichi Ohno.

A root cause method, credited to Taiichi Ohno of the Toyota Production System, in which an investigator asks "why" repeatedly about a failure and each successive answer, continuing past the first plausible explanation until the chain reaches a structural condition that a specific engineering or process change can correct.