5 Whys

5 Whys? is a root cause technique for digging below the surface of an observation or problem to explore the cause-and-effect relationship. It promotes greater understanding of an innovation project and avoids pursuing the wrong issue.

The method was originally developed by Taiichi Ohno in the 1950’s as part of the Toyota Production System; famous for developing key ideas in total quality management and continuous improvement.

The idea is simple. When faced with a problem, such as a test failure, don’t just accept that it happened, ask why it happened. And when you have an answer to what the immediate cause was, ask why again. Keep on asking why until you are getting no more useful information. Like peeling an onion, you progressively strip away the layers until you reach some root causes.

The next step to solving the problem, or the next action to take, may relate to any of the layers, but by drilling down to underlying issues you see where to invest resource for best effect.

In order to carry out the 5-Why analysis properly, the following advice should be followed:

  • Ask the question "Why" until the root cause is determined.
  • Engage as many people in the 5Whys process in the company (including management).
  • Use paper or whiteboard instead of computers.
  • Make our answers precise.
  • Make sure that all people understand and agree on the answers.
  • Distinguish causes from symptoms.
  • Make sure that root causes certainly lead to the mistake by reversing the sentences created.
  • Don't jump to conclusions.
  • Base our statements on evidence.
  • Assess the process, not people.
  • Never leave "human error" as the root cause.
  • Foster an atmosphere of trust and sincerity.