Root-cause confirmation and prioritization

Learning objectives

• Combine triangulated evidence to confirm a root cause.
• Rank confirmed causes by effect, confidence and controllability.
• Distinguish causes, conditions and symptoms.

Confirmation criteria

• Process observation supports the mechanism.
• Temporal order is right (cause precedes effect).
• Association / test / model / experiment agree.
• Removal reduces Y; reappearance restores it.

Garment-factory example

Needle age is confirmed when defect risk rises after a cycle threshold across styles, mechanism matches damage, and a controlled replacement schedule reduces failure without harming output.

Method

1. Build an evidence table per candidate X.
2. Rate strength, effect and controllability.
3. Challenge alternative explanations and confounders.
4. Approve vital few Xs for Improve.

Common mistakes

• Prioritising by brainstorming vote.
• Calling uncontrollable labels ‘root causes’.