What is the 5-Whys Root Cause Analysis Process?

The 5-Whys method is about as simple as its name suggests: Ask why five times, and you’ll likely arrive at the root cause. It utilizes conditional if/then logic.

It was originally used at Toyota as a way to help line workers drill deeper into production issues. The goal is to drive past symptoms to get into the underlying causes. Addressing these causes will be more likely to ensure the problem does not happen again.

But why five whys? Why not four or six? The name is not meant to be taken literally, although it often is. By providing a fixed number (five), it eliminates what would otherwise be ambiguous interpretations.

How Do You Use the 5-Whys Root Cause Analysis Method?

The 5-Whys method is based on the simple rule of conditional logic that follows the pattern “If..., Then...” For instance, if I knock over my cup of tea, then the tea will spill. And its opposite is also true: If I don’t knock over my cup of tea, it will not spill.

But the 5-Whys takes it further than that, identifying precedents to each cause. By looking at preceding causes, the 5-Whys introduces time into the model. The introduction of time is a fundamental difference between the 5-whys and Fishbone RCA model.

The underlying premise is if you go backward in time to uncover preceding causes, you will eventually find the “root cause.” If you control the “root cause,” then you solve the problem.


What are the Benefits of 5-Whys Process?

The 5-Whys is easy - anyone can use it or explain it. The 5-Whys helps teams quickly drill into the underlying causes of a problem. And the 5-Whys is helpful. By examining precursors, the 5-Whys improves understanding and the process of identifying a solution.

What are the Drawbacks to the 5 Whys Process?

The 5-Whys is overly simplistic. Because it does not take into account that causes often work together, it typically does not identify complete causal relationships. Also, it tends to focus mostly on causes associated with people while leaving many of the other necessary causes unaddressed.

Does Sologic Use the 5-Whys?

The Sologic method utilizes the conditional if/then logic of the 5-Whys method, but with some important modifications. First, we eliminate the arbitrary need to drill five levels deep. And second, we add AND/OR logic to the diagram, similar to what would be found in a Fault Tree Analysis.

More on the Sologic RCA Method