5 Why

The method finds the causes of a problem, and works out how the problem can be removed. Its great virtue is that it is simple.

Sakichi Toyoda introduced it, and it is part of the Toyota Production System. It is used all over the world.

When to use it

When what you want is the real, systemic cause of a problem that has happened recently.

When not to use it

  1. When you still do not understand what exactly happened; see 5W+H.
  2. When the problem has several different causes; see the Ishikawa diagram.

How to use it

5 Why is a simple method, and you can bring it in quickly.

1. Ground rules — what to keep in mind

  1. That you are trying to answer two questions:
    1. Why did the problem happen?
    2. Why did nobody notice?
  2. That mistakes come out of a faulty organisation or way of working — the problem is not one person's doing, and so...
  3. ...what you are looking for is a systemic fix, one with enough safeguards in it.

2. Gathering information

You can start by asking the 5W+H questions: Who? What? When? Where? Why? How?

If you need to convince the team that the problem matters, gather a little more:

  • What does the problem cost?
  • How big is it?
  • How many defects?
  • What is at risk?

3. Running the meeting

  1. Define the problem clearly. DESCRIBE THE PROBLEM VERY CLEARLY.
  2. Let the team paraphrase it, to see whether it has been understood as clearly as you think.
  3. Go through the ground rules from point 1.

4. Why?

Ask: why did <the problem, as defined> happen? Write down what comes out.

When you have an answer, ask: why did <that answer> happen? Write down what comes out.

Ask Why about five times.

The goal: used well, the tool should surface the one cause worth setting out to remove.

5. Checking

Does the cause you reached in the last step STILL answer the problem from the first one?

If it does not, go back through the steps with the team. Somewhere in the chain there is a mistake, or a leap too far.

Is the cause you reached in the last step one that can actually be removed?

If it is not, go back through the steps with the team. Somewhere in the chain there is a mistake, or a leap too far.

6. Strategies for removing the cause

Talk through the ways of getting rid of the cause systemically. Write them down. Putting them into the system is your job.

Use it in TeamKit