“The Toyota production system has been built on the practice and evolution of this scientific approach. By asking and answering ‘why’ five times, we can get to the real cause of the problem, which is often hidden behind more obvious symptoms.”
The 5 Whys is a technique for performing iterative questions, used to explore the cause and effect relationships underlying a particular problem.
The main objective is to determine the root cause of a defect or a problem by repeating the question “Why?” . Each answer forms the basis of the next question. The “5” in the name is derived from the empirical observation in the number of iterations typically required to solve the problem.
It was originally developed by Sakichi Toyoda and was used in the Toyota engine corporation during the evolution of its manufacturing methodology.
Not all the problems have a single root cause if one wishes to discover multiple root causes, the method must be repeated, asking a different sequence of questions each time.
The method does not provide simple or strict rules about which lines of questions to explore or how long to follow the search for additional root causes. Therefore, even when the method is carefully applied, the result still depends on the knowledge and persistence of the people involved.
The questioning of this example could be deepened to a sixth, seventh, or higher level, but five iterations of asking why it is generally sufficient to reach one of the causes. The key is to encourage the problem solver to avoid assumptions and logical pitfalls and instead trace the chain of causality in direct increments of the effect through any of the layers of abstraction to one of the causes that still has some connection to it.
It is interesting to note that the last answer points to a process. This is one of the most important aspects of the “5 why” technique because the real root cause must point to a process that is not working well or does not exist. Untrained facilitators often observe which answers seem to point towards classic answers As there is not enough time, there are not enough investments, or there is not enough manpower. These answers may be true, but they are beyond our control. Therefore, instead of asking the question Why?, You can ask the question Why do I fail the process?
The technique was originally developed by Sakichi Toyoda and was used within Toyota Motor Corporation during the evolution of its manufacturing methodologies. It is a critical component of problem solving training, taught as part of the induction into the Toyota production system. The architect of the production system Toyota, Taiichi Ohno, described the method of the 5 Whys as the basis of a Toyota scientific approach, by repeating the 5 whys, the nature of the problem as well as its solution becomes clear. The tool has had an extended use beyond Toyota, and is now used within Kaizen and Six Sigma.
There are two primary techniques that are used to carry out 5 Why: 5 the fishbone diagram (or Ishikawa diagram) or tabular formats. These tools allow the analysis to branch out in order to provide multiple root causes.