rca-analyst

# Root Cause Analysis Skill

> Evidence-based methodology for isolating true root causes from contributing factors.

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## Core Philosophy

**Root cause analysis is evidence gathering, not solution design.**

The RCA process produces:
- Clear problem definition with failure boundaries
- Complete evidence timeline
- Causal chain with differentiated root cause vs contributing factors
- Prevention analysis (WHAT needs to change, not HOW)

The RCA process does NOT produce:
- Proposed solutions
- Implementation roadmaps
- Prioritization decisions
- Resource allocation

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## The Three Tests for Root Cause Isolation

Most teams conflate **root cause** with **contributing factors**. Use these three tests to isolate the true root cause:

### Test 1: Counterfactual Test
> "If this factor didn't exist, would the failure still have occurred?"

- **Root Cause**: NO - removing it prevents the failure
- **Contributing Factor**: YES - failure would still occur via another path

### Test 2: Sufficiency Test
> "Is this factor alone sufficient to cause the failure?"

- **Root Cause**: YES - this factor alone can cause the failure
- **Contributing Factor**: NO - requires other factors to cause failure

### Test 3: Necessity Test
> "Is this factor necessary for the failure to occur?"

- **Root Cause**: YES - failure cannot occur without it
- **Contributing Factor**: NO - failure could occur without it

### Applying the Tests

| Factor | Counterfactual | Sufficiency | Necessity | Classification |
|--------|----------------|-------------|-----------|----------------|
| True Root Cause | NO (prevents failure) | YES | YES | **ROOT CAUSE** |
| Contributing Factor | YES (still fails) | NO | NO | Contributing |
| Necessary Condition | NO | NO | YES | Enabler |
| Amplifying Factor | YES | NO | NO | Amplifier |

**The root cause is the factor that passes ALL THREE tests.**

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## Five-Phase Workflow

### Phase 1: Problem Definition

**Goal**: Establish clear boundaries around what failed