The Fishbone Diagram is the most popular tool for determining root causes. It’ll help you organize your investigation into clues and help you identify the root causes to address to achieve your goal.

The head of the Fishbone is the problem you wish to solve, which is typically based on the Goal Statement, but it may be a sub-problem that contributes to the larger problem. The major "bones" of the Fishbone are the major categories of possible root causes.

These categories can be whatever makes sense but collectively should span every aspect of the process. Examples of some types include 5M (Method, Materials, Manpower, Machine, Measurement) for physical processes, or people, process, equipment, environment, and material for transactional process categories.

Begin by writing the problem to be overcome in the “head” of the diagram. Then decide on the major “bones” or categories of causes. Populate these major “bones” by reviewing all the clues identified, attaching the cause suggested by the clues on the appropriate “bone.” Continue until you’ve used all clues. Then ask yourself, “What else might cause the problem?” This is based on logic and knowledge of the process.

Some people talk about “brainstorming” causes, but that’s not a good approach. Brainstorming is fine for solutions, where even a “wild and crazy” idea might lead to an innovative solution. But the identification of root causes should be done with care. Avoid going down paths that aren’t consistent with how the process functions.

Once you’ve created a framework, convene a group of people who understand the process (along with a few “fresh eyes”) and review your clues, identifying what possible root causes they may suggest. Add to this any other ideas that arise in your discussion. Add each idea as a “bone” attached to the main “bones.” Then, try to dig deeper by asking “why?” to each “bone” you add, attaching bones that further describe the potential causes.

Keep going until all ideas are exhausted, then identify a small number of the potential causes you’d like to take further and circle them. Typically there are five or fewer, but don’t limit yourself if you feel strongly about them. Enter your choices in the “Root Cause Theories” section.

Kure begins to direct you to find root causes right from the beginning by guiding you to look for clues during your process walk and through a review of your data. You’ll build a list of clues before you begin your Fishbone Diagram.

Assemble your team to tackle the Fishbone — you may want to include others beyond your project team — anyone with process knowledge that might shed some light on what’s causing the problem.

When you start the Fishbone Diagram, the problem will already be listed in the head. Then you’ll need to decide on the names of the major “bones.” If you can only think of a few, that’s alright — you can add more as they come to mind.

Kure will display your list of clues, which you can drag onto the major “bone” that’s the best fit. Now think about what that clue may be suggesting as a cause, and edit the wording to describe it better. Next, repeat for all your clues, and then try to think of other possible causes based on your knowledge of the process.

By utilizing Fishbone Diagrams, you can effectively organize your investigation across multiple major categories, enabling you to pinpoint several root causes to address.

Q: Why is the Fishbone Diagram important in Lean Six Sigma?

A: A Fishbone Diagram is important because it helps you visually organize all potential causes of a problem, ensuring you focus on the true root causes rather than symptoms or assumptions. By structuring clues across major process categories, it prevents teams from overlooking key factors and supports a more accurate, evidence‑based investigation.

Q: Who should participate in building the Fishbone Diagram?

A: Select team members that understand the process, and consider including people beyond your core project team.

Q: Is there a limit on how many root cause theories I can select?

A: There is no limit on how many root causes you can select; however, make sure to only select root causes that cause the main problem.

Q: Can I edit the Fishbone Diagram after creating it?

A: Yes. You can edit Fishbone diagrams by selecting a category and deleting it by selecting the trashcan icon, or by adding a cause through the Add Cause button.

Kure guides you through each step in creating your Fishbone Diagram by asking simple questions and providing guidance along the way. Powered by our Process Optimization Path® (artificial intelligence), Kure will help you and your teams collaborate to complete process improvement projects together.