Root Cause Test: How to Tell If You’ve Reached a Root Cause

What is a Root Cause?

Before you can apply a root cause test (several of which are described below), you probably should adopt a definition of a root cause…

Historical Definition of a Root Cause:
The most basic cause (or causes)
that can reasonably be identified
that management has control to fix
and, when fixed, will prevent
(or significantly reduce the likelihood of)
the problem’s recurrence.

The above definition was the one we created in the 1980s. In 2008, we publish a new definition in the TapRooT® Book…

Modern Definition of a Root Cause:
The absence of a best practice
or the failure to apply knowledge
that would have prevented the problem.

For a whole article about the definition of a root cause, CLICK HERE.

Now that you have a root cause definition, you are ready to learn a test to tell if you have reached a root cause (or root causes) when performing an investigation.

How Can You Tell If You’ve Reached a Root Cause?

Some root cause analysis tools don’t give you much guidance when deciding if you’ve reached a root cause. Therefore, you need a root cause test to tell how far you need to dig.

For example, if you use the 5-Why technique, you have reached a root cause when you ask “Why?” five times. But some people say that five is not a magic number. You may need to ask “Why?” more or less than five times. I’ve even seen a 17-Why example. So how do you know if you have reached a root cause? You use a root cause test.

The Washington State Office of Financial Management’s root cause test for a 5-Why root cause analysis is:

When you reach a circular answer like
“because that’s just the way it is”
then you have likely reached the root cause.

I’ve also seen this test:

Dig until you’ve found the “underlying” cause.

People who suggest this root cause test usually give one or two examples of what they think are underlying causes. After that, it’s up to you to decide.

Some expand the explanation of the test above by saying the underlying cause must be a “management system” cause.

Another root cause test that some people recommend is to dig past the symptoms until you get to the “true” causes. Once again, you must decide what a true cause is.

Another root cause test for the 5-Why technique is to ask why until the fix is obvious.

I’ve even seen someone recommend the “trial and error method” for testing root causes. What do you do?

1. Ask “Why” until you think you have reached a root cause that you can fix.
2. Then you implement a fix.
3. If the problem doesn’t repeat, you found the root cause.
4. If it does repeat, you didn’t find the root cause, and you need to go back and ask more whys.

The American Society for Quality provides this advice in a video on their website…

First, consider these three factors to see if you have reached a root cause:

1. RELEVANCE – How relevant are the questions and answers to the original cause or effect that you are investigating?
2. CONTROLABILITY – Did you find a root cause that actually helps control or avoid the situation?
3. SIGNIFICANCE – Are the questions and answers significant enough considering the project scope?

ASQ also provides another tip. Stop asking why when the answer is a process, policy, or person. They say that often these types of answers when you ask why are often root causes.

I Don’t Like These Root Cause Tests

I don’t like any of these root cause tests!

These suggestions are based on your judgment and knowledge. Since different individual’s judgment and knowledge are different, there is no consistency in testing root causes.

If root cause analysis isn’t repeatable and consistent when used by different people, it isn’t consistently finding root causes.

What should you do?

Advanced Root Cause Analysis

Instead of wondering if you have reached a root cause, you could use a system that guides you to root causes and tells you when you have reached a root cause. What root cause system does this?

TapRooT® Root Cause Analysis

TapRooT® Root Cause Analysis addresses all the fundamentals of root cause analysis with advanced techniques.

TapRooT® Root Cause Analysis is the only system with the TapRooT® Root Cause Tree® and Dictionary.

The top of the Root Cause Tree® Diagram is shown above. It leads you to the root causes on the back side of the tree. A sample of a root cause, Lights Need Improvement, is shown in the Human Engineering Basic Cause Category below.

All of the root causes and the process for using the TapRooT® Root Cause Analysis System are documented in the TapRooT® Books and the Root Cause Tree® Dictionary.

Thus, the TapRooT® RCA System doesn’t require a root cause test.

Find Out More About TapRooT® Root Cause Analysis

Here’s a video of Mark Paradies discussing TapRooT® Root Cause Analysis with Kathy Ireland…

Or CLICK HERE to download a paper explaining how TapRooT® Root Cause Analysis works.

TapRooT® Training Information, Dates, and Locations

For more information about the training that can teach you advanced TapRooT® Root Cause Analysis, CLICK HERE.

And to see the dates and locations of our upcoming public TapRooT® Training, CLICK HERE.

We hope to see you at one of our TapRooT® Root Cause Analysis Courses being held around the world so you can use root cause analysis to prevent a serious incident.