Root Cause Analysis – 5 Whys

Why Anyone who has kids or occasionally interacts with five-year olds knows about their uncanny ability to exhaust all your justifications simply by asking “Why”?

Interestingly enough, this characteristic that we often find exasperating in an infant is quite a powerful tool for identifying root causes of problems. As a “tool” it’s quite simple to understand and to use.


  1. Identify the problem under analysis;
  2. Ask “why” and obtain an answer;
  3. Keep asking “why” to each answer until you find the root cause (when the only answer you can come up with is “Just because!”, that’s probably the root cause);

The beauty and applicability of this technique lies in it’s utter simplicity. Granted it’s just useful for root cause analysis, but understanding root causes is often more than halfway home in solving a problem.

This technique is called the “Five Whys” not because you should only ask the question five times, but simply because more often than not five iterations are sufficient to reach a root cause. Here’s a quite quick example of this technique in action:

Problem: My project is behind schedule


  1. Why?
    Because we couldn’t deploy the software on time
  2. Why?
    Because we had integration errors in three components
  3. Why?
    Because they weren’t integration tested
  4. Why?
    Because we don’t have the proper testing environment
  5. Why?
    Because the email ordering the machines wasn’t sent on time

This technique is said to have been invented by Sakichi Toyoda, Japanese inventor, industrialist and founder of Toyota Industries. However, I believe kids throughout the ages might have gotten it even before that.


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