Five Whys Methodology

Philosophical Foundation

Taiichi Ohno: "By repeating why five times, the nature of the problem as well as its solution becomes clear."

Core tenets: scientific evidence-based investigation | address fundamental causes not symptoms | solve to prevent recurrence | use findings for Kaizen

Multi-Causal Investigation

Complex problems have multiple root causes. Investigate comprehensively:

• Parallel: investigate all symptoms/conditions simultaneously
• Branch: follow each cause through all five WHY levels
• Cross-cause: ensure multiple causes don't contradict
• Comprehensive: address all root causes, not just primary

WHY Level Definitions