Root cause analysis is intended to determine the underlying cause of an incident, not the proximate cause. The Japanese have long followed a procedure for getting at root causes that they call the “Five Whys,” originally developed by Sakichi Toyoda and used by the Toyota Motor Company as part of the Toyota Production System for improving quality. Today it is widely deployed. Basically, it means that when searching for the reason, even after you have found one, do not stop: ask why that was the case. And then ask why again. Keep asking until you have uncovered the true underlying causes. Does it take exactly five? No, but calling the procedure “Five Whys” emphasizes the need to keep going even after a reason has been found.
A good passage from the book that details our attitudes towards underlying causes of problems. Too many times, we discover issues and trace it back to human error, and just leave it at there. However, if we were to consider the human as part of an overall system, we should then investigate the conditions and circumstances that would compel for the error to be made.
The “Five Whys” by Toyota is a good heuristic trick that can force us to go further beyond and truly understand the “root cause”.
