114 Root Cause
The key initiating cause in a sequence of events that leads to an event of interest.
• Most problems, especially difficult problems, have multiple causes, and their proximal causes are rarely their root causes. The root cause is the key event in a cause-event sequence that leads to a problem.
• Asking “why?” an event occurred five times (plus or minus) is an effective way to identify root causes.
• For example: Why did the welder burn herself? She wasn’t wearing protective clothing. Why wasn’t she wearing protective clothing? It was hot in the room. Why was it so hot? The air conditioner was broken. The root cause of the accident was a broken AC.
• Focus on root causes when troubleshooting problems. Use the five whys technique to identify root causes and other elements in the causal chain. Since asking why can lead to infinite regress, focus on actionable causes that create the majority of the effects.
See Also 80/20 Rule • Confirmation Bias • Errors • Visibility
