Technique

The “Five Why”-technique was invented in the 1930s by Sakichi Toyoda, a Japanese inventor and industrialist. It was later popularized and refined by Taiichi Ohno, who is considered the architect of the Toyota Production System.

The goal of the technique is to get closer to the root cause of a problem that has been raised and is simple and effective:

1. Identify the problem: Clearly define the issue you want to explore.
2. Ask “Why?”: Ask why the problem is occurring and write down the answer.
3. Repeat: For each answer, ask “Why?” again, digging deeper each time.
4. Continue: Continue this process until you’ve asked “Why?” five times. This helps uncover the underlying cause.
5. Address the root cause: Once identified, take action to address the root cause rather than just treating the symptoms.

The output of this question technique are more concrete assumptions about the root cause as starting point for further explorations. Five means that the “why?” question is asked repeatedly. It can also be less or more than five times.

Examples