5why-root-cause

# 5-Why Root Cause Analysis ## Goal Identify and validate a systemic root cause through a structured, evidence-based Why chain that can be directly linked to a corrective action. ## Required Execution Checklist - [ ] Problem defined with measurable data (value vs. specification) - [ ] Linear Why chain built — one cause path at a time, no branching - [ ] Each Why supported by objective evidence (not opinion or "probably") - [ ] Logical consistency verified — reversal check passed - [ ] Systemic root cause identified (not "human error" or symptom) - [ ] Root cause validated: reproducibility test + elimination test - [ ] Output enables definition of corrective action (PCA or CAPA) --- ## When to use Use 5-Why for any quality problem with a single, linear cause chain. Works best for process failures, equipment failures, and procedural non-compliances. For complex problems with multiple contributing causes, use [Fishbone](../fishbone-analysis/) first to identify candidate root causes, then use 5-Why to drill into each. If multiple potential cause paths exist — do not combine them into one chain. **Run separate 5-Why chains for each path** and determine which is confirmed by evidence. ## Prerequisites - Problem is clearly defined (use [Is/Is-Not](../is-is-not-scoping/) to scope if needed) - The investigation team has access to the process, machine, or system where the defect occurred - Physical evidence or production records are available ## Use within 8D — Occurrence an...