February 5, 2020 | Barb Carr

“Fast” Root Cause Analysis: Brainstorming, 5-Whys and Fishbone Diagrams

Brainstorming, 5-Whys and Fishbone Diagrams are “go-to” root cause analysis techniques for many investigators because they are simple to learn and apply. That sounds really nice, but do they really do the job? Let’s take a look at each “fast” root cause analysis technique.


Brainstorming is a group process. Everyone in the group gives an idea in rotation (or passes his/her opportunity to give an idea) until the next round. It’s kind of like the child’s card game, “Go Fish.” Even a kindergartener can do it! Some believe that the benefits of brainstorming are collecting different viewpoints and encouraging a deeper level of critical thinking. These are good activities, but is that really root cause analysis?

Without evidence proving the problem occurred, and a structured way to analyze the problem, the wrong root causes may be selected and/or not all of the root causes will be identified. You will also not be able to get beyond the collective knowledge and experience of the team. When these things happen, the wrong corrective actions are developed, and the same problems arise again.


Let’s conduct a fast 5-Whys investigation! First, we’ll assemble the investigation team. After that, we’ll define the problem. (“The company vehicle will not start.”) Then, we’ll ask the first ‘why.” “Why is the company vehicle not starting?” To wrap it up, we’ll ask “why” four more times, framing each “why” in response to the answer we’ve just recorded. It looks like this:

Problem: The company vehicle will not start.

Why? The battery is dead. (First why)

Why? The alternator is not functioning. (Second why)

Why? The alternator belt has broken. (Third why)

Why? The alternator belt was well beyond its useful service life and not replaced. (Fourth why)

Why? The company vehicle was not maintained according to the company policy. (Fifth why)

Is not maintaining the company vehicle according to policy a root cause? That sounds like a problem but I would not call that a root cause.

  • Have you looked at the company policy and does it need improvement?
  • Does the person responsible for maintaining the vehicle know he/she is accountable to maintain it?
  • Is compliance with the maintenance schedule being enforced?

None of these questions were brought up during the 5-Whys investigation but they are significant to determine a true root cause.

According to TapRooT®, a root cause is “the absence of a best practice or the failure to apply knowledge that would have prevented the problem.” So, we would consider maintenance not being performed on the vehicle a problem that would need to be analyzed for root causes but we would not consider that a root cause.

5-Whys isn’t just simple, it’s dangerously simplistic . . . meaning we don’t learn very much from the incident. Incidents are seldom the result of a single root cause, and users of ‘5 whys’ are limited to one root cause per causal pathway.

Fishbone (Ishikawa) Diagrams

Fishbone employs brainstorming and may also pull in 5-Whys. It’s more organized. The group brainstorms possible causes of a problem, then rates the potential causes according to level of importance and creates a hierarchy diagram that looks like the skeleton of a fish.

The head of the fish is created by listing the problem in a statement format. A horizontal arrow is drawn behind the head with the arrow pointing to the head creating the fish’s “backbone.”  Fishbone diagrams are worked right to left, with the large “bones” of the fish branching out to include smaller bones containing more detail. At least four “causes” are identified and branched off on the smaller bones. For each cause, a questioning method like 5-Whys or the 4P’s (Policies, Procedures, People and Plant) are used.

So on the surface, it looks like a better, more organized system. But is it good root cause analysis? It’s helpful to draw the diagram and think through possible causes. However, it’s the word “possible” that’s troubling. What if the causes chosen are not the right causes? What if you forgot one from the list? What’s keeping an investigator from falling into the trap of his/her own bias?

Fishbone diagrams provide structure for hypotheses but they do not provide answers.

TapRooT® Root Cause Analysis

If you would like to learn about how to avoid:

  • fixing problems and not root causes
  • selecting the wrong root causes
  • being trapped in bias
  • being limited by the knowledge and experience of your team to develop root causes

consider TapRooT®.

TapRooT® Root Cause Analysis is a patented and proven method of stopping human error through a systematic process.

Learn more or register for 2-day TapRooT® Root Cause Analysis training.

Investigations, Root Cause Analysis
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