Root Cause

Scenario: Some bad event B happens in a manufacturing environment.

A root cause investigation is conducted and it is determined that R is the root cause (or set of causes) of B.

Corrective action (or set of actions) C is taken to eliminate the possibility of R occurring again.

Yet the same bad event B happens 3 months later.

What happened?

There are three possibilities:

1. C wasn't implemented correctly
2. C doesn't really eliminate the possibility of R
3. R isn't really the root cause of B

Options 2 and 3 often aren't considered.