Lean manufacturing and the Toyota Production System

2. Charg� de cours : Pierre Simard Pierre Simard Samson, Loiselle et Associ�s 1187, des �perviers Longueuil (Qu�bec) J4G 1Z9

20. Five Whys The Five Whys is a question asking method used to explore the cause/effect relationships underlying a particular problem. Ultimately, the goal of applying the 5 Whys method is to determine a root cause of a defect or problem This technique explores deeper and deeper levels until one gets to a level where proactive counter-measures can be applied. It does not necessarily equate to 5 levels. It may be more or less depending on the case. The five whys is a question asking method used to explore the cause/effect relationships underlying a particular problemThe five whys is a question asking method used to explore the cause/effect relationships underlying a particular problem

21. Five Why's example The car does not start Why? - The battery is dead Why? - The alternator is not functioning Why? - The alternator belt has broken Why? - The alternator belt was well beyond its useful service life and has never been replaced Why? - I have not been maintaining my car according to the recommended service schedule

22. Five Whys Difficulties This technique is more difficult to apply then it may seem at first. Naturally people tend broaden the potential causes at one level instead identifying the main cause and going to a deeper level of causality. i.e. They find many superficial factors instead of digging to the root cause. More often than not going to a deeper level requires further investigation (more data, interviews etc.) i.e. You don't go to the deepest levels in one 5 minute conference room session. This technique is limited by the knowledge the participants have. For this reason it works best when there are participants with varied expertise and good investigation technique.