Root Cause Investigation Methodology
Pioneered by Taiichi Ohno at Toyota, 5-Why analysis systematically strips away layers of symptoms to expose underlying institutional defects.
Foundational Category: Root Cause & Risk • ~4 min read
5-Why Root Cause Tree
Drill past superficial symptoms to uncover systemic and management process root causes.
Q:
How do you prevent 5-Why analysis from turning into superficial blame?
Follow the 3-tier causality model: move past the Physical Cause (part broke) and Human Error (valve left closed) to identify the Latent / Organizational Root Cause (management process, training, or audit omission). Always apply the reverse "Therefore" test to ensure logical rigor.
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RCA Auditor Evaluation:
Good investigation depth.
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Engineering & Regulatory Notice: The calculations, projections, and failure models provided in this suite are for engineering estimation and educational purposes. Verify all calculations and assumptions independently before making operational, equipment replacement, safety-critical, or regulatory compliance decisions.
Recommended Next Steps in Reliability Workflow
Root Cause & Risk
Ishikawa Fishbone Diagram
Map all potential causes across Machine, Method, Material, Manpower, Measurement, and Milieu.
Root Cause & RiskFMEA / FMECA Risk Worksheet
Rank system failure modes by risk priority and assign mitigation actions with XLSX/PDF exports.
Root Cause & RiskCorrective Action Tracker (CAPA)
Ensure root cause corrective actions are implemented, verified, and closed out on time.