5 Why techniques

The "5 why" technique (also call "ladder of whys" or "the 5 whys") is a method base on questions to explore cause and effect relationships that generate a problem in particular. The ultimate goal of the 5 Why is to determine the cause of a defect or problem root.

Today we are going to study it in a different way through the analysis of root cause (ACR or RCA) in its acronym in English: method for the resolution of problems that tries to avoid the recurrence of a problem or defect through identifying their causes.

To enter already in the field, we are going to start giving a definition of what is this technique.

The technique was originally develop by and was use in the Toyota Motors Corporation during the evolution of their manufacturing methodology. This technique appears in other forms in other companies. Under the direction of Ricardo Semler, Semco uses three "why?" and extends the practice for the determination of goals and decision-making.

Is base on a process of traceability, analyze the possible causes to the problem walking backwards. Until you get to the last cause that originate the problem. Take into account that they do not have to be exactly 5 questions. As this will depend on the length of the causal process of the problem.

Objectives of the techniques

The objective of this technique is to discover vital information in a systematic way, analyze the hidden causes and develop solutions to the questions raise. It can be apply to the resolution of a conflict, take of diagnosis or decision making.

Are going to see the development of this technique as well as the final outcome obtain using the following simple example:

The technique is simple, has no great difficulty of application, is an easy and often effective tool for discovering the root of a problem. It is simple, can be tailor quickly so that you can resolve almost any issue, so we must make it out and apply it whenever it is necessary

when looking to solve a problem, begins with the final result of the situation that you want to analyze and work backwards (toward the root), continuously question:

"why?". Repeat one and again the question until the root cause is evident.

Example: A machine is broken.

1. Why have I stop the machine? -Jump the fuse due to an overload.


2. Why was an overload there? -By inadequate lubrication of the bearings.


3. Why was the lubrication inadequate? -Lubrication pump did not work well.


4. Why did not work well the lubrication pump? -The pump shaft was worn.


5. Why was the pump shaft worn? -It had enter dirt inside.