5 Why Analysis – History & Methodology

PowerPoint · 10 slides · English · Incident Investigation

A concise visual guide explaining the history, methodology, worked example, rules, strengths and limitations of the 5 Why Root Cause Analysis technique.

By Saurabh Rawat · Published 2026-09-29 · Updated 2026-11-12

From the document

5 WHY ANALYSIS History & Methodology A root-cause investigation technique from Toyota's shop floor to modern quality management THE EHS GURU WHAT IS 5 WHY ANALYSIS? A simple, iterative interrogative technique used to explore the cause-and-effect relationships underlying a specific problem. 01 Ask “Why?” repeatedly Typically five times, until the true root cause surfaces 02 Root cause, not symptom Digs past the obvious fix to the underlying system failure 03 Simple & low-cost No statistical tools needed — just structured questioning HISTORY The Origins — 1930s Sakichi Toyoda Founder of Toyota Industries Developed the 5 Why method in the 1930s as part of his approach to problem-solving on the factory floor. Applied it while refining his automatic textile looms — tracing defects back to their true origin rather than the nearest visible cause. The technique became one of the founding practices of what would later be called the Toyota Production System (TPS). 1930s HISTORY Formalized in the Toyota Production System Taiichi Ohno In the 1950s–70s, Taiichi Ohno — architect of the Toyota Production System — formalized and popularized the 5 Why technique. Described it as “the basis of …

5 why analysis · 5 whys · root cause analysis · rca · accident investigation · incident investigation · problem solving · ehs · occupational safety · toyota production system

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