root-cause-analysis

Root Cause Analysis

Role: structured incident investigation. Tradition: TPS / Ishikawa / Reason / Gano / Google SRE.

Five methods

1. 5-Whys

Linear or branched cause chain. Good for simple, single-thread incidents.

Why did X happen? → Y
  Why did Y happen? → Z
    Why did Z happen? → W
      Why did W happen? → V
        Why did V happen? → U  (root cause)

2. Fishbone (Ishikawa, 6 Ms or 4 Ps)

Good for multiple suspected cause-areas at once.

6 Ms (manufacturing tradition):

• Method
• Material
• Machine
• Manpower
• Measurement
• Mother Nature / Milieu

4 Ps (service tradition):

• People
• Process
• Policy
• Plant/place

Output as mermaid or hierarchical list.

3. Postmortem (blameless timeline)

Good for complex incidents with multiple actors. Wraps other methods.

Structure:

1. Timeline — what happened, when, by whom (without blame)
2. Triggering events — direct triggers
3. Contributing factors — structural conditions
4. Root cause analysis — uses 5-whys or fishbone
5. Action items — what's done differently next time (with owner + deadline)
6. Lessons learned — what to preserve in the organisational memory

4. Fault Tree (AND/OR gates)

Good for safety-critical multi-path failures.

Top event (undesired outcome) → backward via logic gates:

• AND gate: all sub-outcomes must occur
• OR gate: any sub-outcome suffices

Identifies minimal cut sets — smallest combinations leading to failure.

5. Kepner-Tregoe IS/IS-NOT

Good for subtle, hard-to-reproduce defects. Distinction analysis.

	IS (when the problem occurs)	IS-NOT (when the problem doesn't occur)
What	...	...
Where	...	...
When	...	...
Scope	...	...

The distinction between IS and IS-NOT reveals what's specific about problem cases.

Method selection

Problem type	Recommended method
Simple cause-effect	5-Whys
Several possible cause areas	Fishbone
Complex incident with timeline	Postmortem (wraps others)
Safety-critical with multi-path	Fault tree
Subtle, hard-to-reproduce	Kepner-Tregoe IS/IS-NOT

Domain examples

Question	Method	Insight
"Why does digital transformation fail in organization X?"	Postmortem + Fishbone	Multiple contributing factors: leadership, tech, culture, finance
"Why wasn't the policy implemented?"	5-Whys	Political will → funding → administrative capacity → root cause
"Why is online discourse polarising?"	Fault tree	AND gate: algorithm + lack of media literacy + social incentives
"Project was late — one-off or pattern?"	IS/IS-NOT	Which weeks ship on time? What differs?

Core axioms (must be applied)

1. People are never root causes. If a human could make the error, the system permitted it. "Why was the person able to make this mistake?"
2. A cause is 'root enough' when actionable. Stop when you reach the point where intervention can actually happen.
3. Proximate cause ≠ root cause. The visible trigger is where analysis begins, not ends.
4. Non-blameful tone. Goal: learn from system failure, not find a scapegoat.

Integration with other skills

• thinking-science for hypothesis generation during investigation ("what if the cause was X?")
• thinking-redteam for stress-testing remediation proposals (will it actually work?)
• systems-thinking for structural loops (complementary — RCA is linear, systems-thinking cyclic)

Output format

• 5-Whys: linear list with arrows
• Fishbone: mermaid or text hierarchy
• Postmortem: structured markdown with 6 sections
• Fault tree: mermaid
• Kepner-Tregoe: table

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🎯 COMPLETED: [SKILL:root-cause-analysis] [RCA on event X] 🗣️ CUSTOM COMPLETED: [SKILL:root-cause-analysis] [RCA done]