5xWhy

5xWhy is a problem-solving technique used to uncover root causes by repeatedly asking why a problem occurs. It is closely related to the Five Whys method and is used across manufacturing, software development, and service delivery to move beyond symptoms and understand underlying processes. The approach is associated with lean management and Toyota's quality improvement practices; however, the exact term 5xWhy is used variably by organizations to describe the same iterative questioning process.

A team defines a concise problem statement and then asks why the problem happened. The answer becomes the basis for the next why question, with each successive answer forming a chain. The process typically proceeds for five iterations, but teams may continue beyond five questions if needed to reach a credible root cause. Documentation of the reasoning, cross-functional input, and supporting data help validate each step and prevent misinterpretation. Once a root cause is identified, countermeasures are proposed and tested for effectiveness.

Benefits include simplicity, speed, and the way it encourages collaboration to surface process weaknesses. The method also risks stopping at a proximate cause if questions are poorly framed or data is incomplete, and it may be less effective for complex systems with multiple interdependent factors. It should be used with clear problem scoping, evidence collection, and, when appropriate, integrated with other tools such as root-cause diagrams.

Relation to other methods: Five Whys is often discussed alongside Ishikawa diagrams, fault tree analysis, and other root-cause techniques. Some uses of the term 5xWhy treat it as an interchangeable variant of Five Whys, while others emphasize an expanded or multiplicative framing of the questioning process. The core idea remains iterative questioning to reveal deeper causes.