Fishbone Diagram

Also known as a Cause and Effect diagram, or Ishikawa diagram. The method was created by Kaoru Ishikawa in the 1960’s. He created it to help employees avoid solutions that merely address the symptoms of a much larger problem.

The defect or problem is shown as the fish’s head on the right side (typically). The major categories or causes of the problem or defect are the ribs off the fish’s backbone.

The most common categories are the 6 M’s:

• Manpower (People)
• Methods (Processes/Procedures)
• Materials (Supplies/Vendors)
• Machines (Equipment)
• Measurement
• Mother Nature (Environment)

Another concept is 4 P’s:

• Policies
• Procedures
• People
• Plant/Technology

From each rib, additional levels or root causes of each category become branches from the bones.

How to create a fishbone diagram

1. Define the Problem: Write down the problem or effect you want to analyze at the head of the fish (the right side of the diagram).
2. Draw the Backbone: Draw a straight horizontal line (the backbone) pointing to the problem statement.
3. Identify Major Categories: Draw several diagonal lines (the ribs) branching off from the backbone. Use the 6 M’s or 4 P’s from above as a starting point, but feel free to modify them as needed for your process and situation.
4. Brainstorm Causes: For each category, brainstorm potential causes of the problem. Write these causes as smaller lines branching off from each rib. Make sure you invite a cross-functional team to participate to generate as many ideas as possible. We recommend you use AI tools to help you with brainstorming causes for your fishbone.
5. Analyze the Diagram: Review the diagram to identify relationships and prioritize causes for further investigation. You can prioritize using actual data, multivoting, nominal group techniques, or gaining consensus from the team.
6. Determine root causes: Use 5 Whys to breakdown each of the prioritized causes further until you reach the root cause (process breakdown).
7. Take Action: Use the insights gained to develop solutions or action plans to address the root causes identified.

Minitab web-version (included with all standard licenses) has a tool called Brainstorm that allows AI to help brainstorm causes for your problem statement.

You can create this diagram on paper, whiteboard, online collaboration tools (Zoom, Mural, Miro, etc) or use software tools like Microsoft PowerPoint, Lucidchart, Creately (affiliate link), or online diagramming tools for a more polished look.

Creately has multiple templates you can select from.

You can also get a free Creately trial, and options for the paid version for as low as $1 per month.

Update: Microsoft Whiteboard is a free online software that has a Fishbone Diagram template you can use.

For digital transformations, a new revamped Fishbone Diagram was proposed by Darshi Bassi and Marissawith Gentling in ASQ Quality Progress (June 2025).

The new categories are as follows:

• Digital organizational structure
• Digital Infrastructure and technology
• Digital strategy
• Digital culture
• Digital capabilities and talent
• Digital leadership

Q&A

When is a fishbone diagram NOT a good tool to use?

Without a good, clear problem statement, the fishbone diagram will not be effective and will be frustrating for the participants. Although it can be a good tool when data is lacking, it will make it more difficult to decide which causes to pursue and how to validate potential cause-effect relationships when data is not available.

It’s also not ideal for highly complex systems where causal chains and multiple interactions occur, such as supply chain disruptions involving dozens of variables. System dynamics models or fault tree analysis may better capture interactions. The fishbone is more suited for structured brainstorming than for highly technical, multi-layered analysis.

How do you facilitate a brainstorming session to build a good fishbone diagram?

We have put together a list of steps to follow in the section above titled “How to create a fishbone diagram”

How do you decide how many “levels” of causes to include in a fishbone diagram?

In practice, the number of levels is determined by how far the team needs to dig to uncover causes that are actionable. If the first layer of branches simply states symptoms (e.g. “Machine broke down”), then probing into sub-causes (e.g. “Lack of maintenance schedule” or “Worn bearing”) may be useful. Typically, going two to three levels deep is most common. Remember, the fishbone diagram will not determine the root cause. Using a 5 Whys exercise can take that 2nd or 3rd level cause further until you reach a process breakdown.

How do you prioritize or validate which causes are worth investigating further?

A fishbone generates possibilities, not proofs or confirmed root causes. Once you’ve brainstormed causes, prioritization methods like data analysis, multivoting, Pareto analysis, or impact-effort matrices help focus on the most likely contributors. Teams often combine voting with actual and subjective data (such as checking records, measuring defects, or reviewing logs) to validate which causes are real drivers.

Another option is using hypothesis testing or designed experiments to verify suspected root causes. For example, if “operator fatigue” is suspected, you might compare error rates across different shift lengths and types of tasks. The fishbone diagram should not be treated as a conclusion but as a guide for structured investigation.

Can you build a digital/automated fishbone diagram in software, and what are good tools or features for that?

Yes—many digital tools support fishbone diagrams, ranging from general diagramming apps (Lucidchart, Miro, MURAL, Creately or Visio). Digital versions make it easier to collaborate remotely, move branches around, and export diagrams into reports. They also allow for layering, hyperlinks, and attaching data sources directly to causes. You can also use ChatGPT and other AI tools to support brainstorming of ideas, and generate a fishbone from the causes identified.

When choosing a tool, look for features like real-time collaboration, ease of moving items around within the template along with standard fishbone categories, and the ability to expand/collapse branches as complexity grows. Automation can also help when linking the diagram to other problem-solving tools, such as connecting causes directly to corrective action plans or control charts.

How do you use a fishbone diagram in continuous improvement or iterative problem solving (e.g. PDCA cycles)?

In PDCA, the fishbone diagram fits naturally into the “Plan” stage, and the Measure and Analyze phase of DMAIC. It’s a tool for generating hypotheses about what might be causing the problem. Once you identify likely causes, you test countermeasures in the “Do” stage and verify results in “Check.” The diagram then becomes a living document to revisit if initial actions don’t solve the issue. Simply cross off the causes you’ve ruled out (or highlight the ones that are valid) and pursue another cause on your diagram.

How do you avoid common pitfalls or biases when constructing a fishbone?

One common trap is stopping at surface-level causes that merely restate the problem (e.g. “machine malfunctioned”) without probing deeper. Another is confirmation bias where teams list only causes they already believe in, ignoring alternative explanations. To avoid this, facilitators should push for breadth, encourage challenges to assumptions, and ask “why” multiple times (consider 5 Whys).

Another risk is groupthink, where participants defer to senior voices. Consider using anonymous brainstorming methods like brainwriting causes on sticky notes before discussion. This also helps teams . Teams should also supplement brainstorming with data analysis to avoid overreliance on opinion. A strong facilitator keeps the session balanced and evidence-driven.

What are alternative or complementary root cause analysis tools, and when would you choose those over fishbone?

The 5 Whys technique is often paired with or used instead of a fishbone. It’s faster and simpler, good for straightforward problems with one clear effect. Fault Tree Analysis is another option for safety-critical systems, since it shows probabilities and logical dependencies. Tools like scatter plots, regression, or DOE may be better when quantitative relationships are needed on more complex problems.

System mapping tools, such as causal loop diagrams or process flowcharts, can reveal interdependencies and feedback loops that a traditional fishbone diagram misses. FMEA (Failure Modes and Effects Analysis) is stronger when you want to systematically assess risk across many potential failure points. The fishbone diagram is best seen as one tool in a toolkit, not a standalone method.

Is there affordable or low cost training on Fishbone Diagrams and other Root Cause Analysis tools?

We have developed two courses on Root Cause Analysis:

• Intro to Root Cause Analysis (free)
• Advanced Root Cause Analysis

How do you measure or track the effectiveness of solutions derived from a fishbone analysis?

After implementing countermeasures, you need to verify whether the suspected cause was truly eliminated. This means tracking the key performance indicator (data) tied to the effect (e.g. defect rate, downtime, customer complaints) before and after the fix. Ensure that the action plan is well coordinated with other changes to make it easy to determine if you have improved the problem. Control charts, run charts, or simple before-and-after comparisons can confirm whether variation has decreased, and hypothesis tests can be run to statistically validate an improvement in the data.

It’s also useful to revisit the fishbone and mark which branches have been addressed. If the problem persists, then the remaining causes need further investigation. By documenting which causes were tested, which were ruled out, and what improvements held, the team builds organizational learning for future problem-solving efforts. A standard action item tracking form can be used along with documentation on your fishbone diagram on what causes have been eliminated or validated.

Links

• Fishbone Diagram Powerpoint Template
• Root Cause Analysis Online Training
• Ishikawa diagram – Wikipedia
• Fishbone Diagram Online Template from Creately
• Fishbone Diagram Online Template from Mural

Videos