5 Whys
The 5 Whys is a root-cause analysis technique developed by Sakichi Toyoda and refined within the Toyota Production System. By repeatedly asking "Why?" β typically five times β you move from surface-level symptoms to the underlying cause of a problem. Simple, fast, and remarkably effective for operational and interpersonal problems, it is the most widely-used structured problem-solving technique in manufacturing, software, and management worldwide.