Base120 · Decomposition

Root Cause Analysis (5 Whys)

DE · Decomposition

Iteratively ask why problems occur until fundamental cause emerges

Model code
DE1
Transformation
DE (Decomposition) — Break problems into factors, layers, and independent subproblems.
Priority
1 of 20
Framework
HUMMBL Base120 — 120 mental models across 6 transformations

When to use

"Use when a problem's surface symptom differs from its root cause. Iteratively ask why until you reach a cause you can act on. Typically 5 iterations, but the right number is whatever reaches an actionable root."

Example

"The deployment failed. Why? The build timed out. Why? Tests took 40 minutes. Why? The test suite grew without parallelization. Why? No one was assigned to maintain test infrastructure. Root cause — test infrastructure ownership is unassigned. Action — assign ownership."

Common misuse

"Stopping at a cause that assigns blame (the developer made a mistake) rather than a cause that reveals a systemic fix (the review process does not catch this class of error). Root cause analysis is about systems, not individuals."

Also known as

5 WhysRoot Cause Investigation

Related models

DE4P1IN2