What is 5 Pourquoi?

The "5 Whys" is an iterative interrogative technique used to explore the cause-and-effect relationships underlying a particular problem. The primary goal is to determine the root cause of a defect or problem by repeatedly asking the question "Why?". Each answer forms the basis of the next question. The '5' in the name is just a rule of thumb, and the actual number of questions may be more or less, depending on the issue. It is commonly used in lean manufacturing and problem-solving methodologies.