トヨタ生産方式
The technique was originally developed by Sakichi Toyoda and was used within the Toyota Motor Corporation during the evolution of its manufacturing methodologies. It is a critical component of problem-solving training, delivered as part of the induction into the Toyota Production System. The architect of the Toyota Production System, Taiichi Ohno, described the five whys method as "the basis of Toyota's scientific approach by repeating why five times the nature of the problem as well as its solution becomes clear." The tool has seen widespread use beyond Toyota, and is now used within Kaizen, lean manufacturing and Six Sigma. The five whys were initially developed to understand why new product features or manufacturing techniques were needed, and was not developed for root cause analysis.