Pour réellement arriver à corriger un problème, il est primordial de commencer par bien le comprendre. Il faut en trouver les racines. De plus, l’effort supplémentaire pour bien analyser le problème va se payer de lui même en nous permettant de découvrir une solution qui sera souvent plus simple que l’on envisageait au départ.

Dans le livre Toyota Production System, Taiichi Ohno explique qu’il utilise la technique suivante : Répétez « Pourquoi? » 5 fois

Repeating Why Five Times

When confronted with a problem, have you ever stopped and asked why five times? It is difficult to do even though it sounds easy. For example, suppose a machine stopped functionning :

1. Why did the machine stop? There was an overload and the fuse blew.
2. Why was there an overload? The bearing was not sufficiently lubricated.
3. Why was it not lubricated sufficiently? The lubrication pump was not pumping sufficiently.
4. Why was it not pumping sufficiently? The shaft of the pump was worn and rattling.
5. Why was the shaft worn out? There was no strainer attached and metal scrap got in.

Repeating why five times, like this, can help uncover the root problem and correct it. [...] By asking why five times and answering it each time, we can get to the real cause of the problem, which is often hidden behind more obvious symptoms.