The 5 Whys (and Some Limitations)

Why” by Willbryantplz

I came across this video on the Harvard Business Review website called “The 5 Whys.” Sometimes, a video helps explains an idea better/clearer than just written words alone. However, in oversimplifying a concept, we may sometimes leave out a critical analysis of its weaknesses as well as devising strategies to address them.

The 5 Whys or asking why a problem exists five times is borrowed from the Toyota production system (mentioned in the book “The Toyota Way”). The idea is to get to the root cause, by going deeper with each “Why?”, of what caused something to fail (whether it’s a server crash or product that doesn’t work) and then fix that root cause.

“Behind every seemingly technical problem is actually a human problem waiting to be found.” -Eric Ries, entrepreneur-in-residence at Harvard Business School

Had the video used a more interactive graphics that simulates/moves as the speaker is talking, I think that would be even better. That said, here’s the link to that video (sorry, there was no link on HBR to the flash video for WordPress).

5 Whys: Ask 5 Times (here’s an example from Eric’s April 2010 post):

  1. A new release broke a key feature for customers. Why? Because a particular server failed.
  2. Why did the server fail? Because an obscure subsystem was used in the wrong way.
  3. Why was it used in the wrong way? The engineer who used it didn’t know how to use it properly.
  4. Why didn’t he know? Because he was never trained.
  5. Why wasn’t he trained? Because his manager doesn’t believe in training new engineers, because they are “too busy.”

Nothing is a perfect system and the 5 Whys is no exception. In fact, the more I think about asking “why” the more I think back to my time in undergrad studying philosophy. If we’re not careful, we can easily fall into the trap of asking an endless series of hypothetical/conceptual whys with no pragmatic solutions (this was the reason why I switched from philosophy to psychology).

Anderson (2009) had this to say:

“Under a 5 Whys approach, it is possible to get to root causes in a relatively short period of time. However. . .ease of use and speed also need to be balanced with the risk of failure from recurrence of the problem should the 5 Whys fail to find the true root cause.”

Here is Anderson’s critique of the 5 Whys (in his own words):

  • Using 5 Whys doesn’t always lead to root cause identification when the cause is unknown.
  • An assumption underlying 5 Whys is that each presenting symptom has only one sufficient cause. This is not always the case and a 5 Whys analysis may not reveal jointly sufficient causes that explain a symptom.
  • The success of 5 Whys is to some degree contingent upon the skill with which the method is applied; if even one Why has a bad or meaningless answer, the whole procedure can be thrown off.
  • The (5 Whys) method isn’t necessarily repeatable; three different people applying 5 Whys to the same problem may come up with three totally different answers.

Anderson points out that it’s extremely important to understand the difference between root causes and causal factors. “Causal factors are those factors that contribute to the occurrence of a problem, but are not necessarily the initiating cause of a problem—the root cause. Therefore, causal factors and chains need to be analyzed further to determine their root causes.”

“A robust problem-solving method must be adept at not only identifying a problem’s causal factors, but equally adept at uncovering the root causes that underpin the causal factors.” -Stuart Anderson, president of Kaizen Solutions Inc.


Anderson, S. (December, 2009). Quality Digest – Root Cause Analysis: Addressing Some Limitations of the 5 Whys. Retrieved from

HBR – The 5 Whys

HBR – The Five Whys for Start-Ups