The 5 whys principle

The 5 whys principle

In the same way children use “Why?” to build understanding and the links between different things, we too can build understanding of the linkage between problems and the root cause as well as possible solutions for it.

The vehicle will not start. (the problem)

Why? – The battery is dead. (First why)

Why? – The alternator is not functioning. (Second why)

Why? – The alternator belt has broken. (Third why)

Why? – The alternator belt was well beyond its useful service life and not replaced. (Fourth why)

Why? – The vehicle was not maintained according to the recommended service schedule. (Fifth why, a root cause)

The questioning for this example could be taken further to a sixth, seventh, or higher level, but five iterations of asking why is generally enough to get to a root cause.

The Key

The key is to encourage the trouble-shooter to avoid assumptions and logic traps and instead trace the chain of causality in direct increments from the effect through any layers of abstraction to a root cause that still has some connection to the original problem.

Note that, in this example, a solution [quick fix] can be found at almost any level, but the problem will reoccur unless the fifth why is addressed. The fifth why in this example suggests a broken process or an alterable behaviour, which is indicative of reaching the root-cause level.

It is interesting to note that the last answer points to a process.

This is one of the most important aspects in the 5 Why approach – the real root cause should point toward a process that is not working well or does not exist.

Untrained facilitators will often observe that answers seem to point towards classical answers such as

  • not enough time,
  • not enough investments,
  • not enough manpower.

These answers may be true, but they are out of our control.

Therefore, instead of asking the question why?, ask why did the process fail? – this is IN our control

A key phrase to keep in mind in any 5 Why exercise is

people do not fail, processes do“.


Remember there is always…

More Than One Answer