What Is a Fishbone Diagram?

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Learn how to get to the root cause of a problem by creating a fishbone diagram, a powerful project management tool.

[Featured image] A piece of paper shows a fishbone diagram drawn with red, blue, and yellow ink.

A fishbone diagram, also referred to as a cause and effect diagram or an Ishikawa diagram, is a helpful tool for identifying the root cause of a problem. It allows you to list all the potential causes that may be contributing to the effect you are currently experiencing. This visual aid takes the shape of a fish skeleton, hence its name. Project managers commonly use them during brainstorming sessions.

To create a fishbone diagram, organize the possible causes on the left side, categorized by causes. These make up the "bones" of the fish. On the right side, place the effect or problem you are investigating—the "head." This structure provides a quick way to visualize the various causes associated with the effect.

What is a fishbone diagram?

A fishbone diagram, also known as a cause-and-effect diagram, is a visual tool used to brainstorm and categorize potential root causes of a problem. By laying out these causes on a fishbone-shaped structure, teams can effectively identify the most likely reasons behind an issue and implement solutions.

When to use a fishbone diagram

When used effectively, a fishbone diagram serves as an easy-to-interpret schema for root cause analysis. Other benefits of using a fishbone diagram include: 

  • Easy identification of bottlenecks: With a fishbone diagram, you can visually map out interdependencies within your business process, making it easier to spot bottlenecks. When paired with data analysis tools, fishbone diagrams can help you gain deeper insights into operational inefficiencies. 

  • Address and eliminate recurring issues: Identifying the root cause of a problem allows you to address it at its source, minimizing the likelihood of similar bottlenecks recurring in the future. This, in turn, promotes sustained stability and efficiency in your business operations.

  • Clear visualization of shifts in business strategy: Applying a fishbone diagram through multiple iterations of a change allows you to visualize and understand the broader implications of that change on interconnected processes. The iterative approach facilitates strategic adjustments to your business plan.

  • Increased collaboration among teams: Fishbone diagrams promote synergy among team members by offering a medium for brainstorming solutions. The collaborative approach ensures that everyone contributes their insights and perspectives, leading to a more comprehensive understanding of underlying business issues.

Read more: 9 Project Management Trends to Know

How to create a fishbone diagram

Follow these steps to create your own fishbone diagram from the ground up:

1. Provide a problem statement. 

A problem statement is the effect or problem you are investigating and goes in a box with an arrow pointing to it on the right side of a flipchart page, as if forming the head of the fish. Everyone on the team agrees on the definition of the problem.  

2. Define major cause categories. 

Form the skeleton of your fishbone diagram with the major cause categories, which you connect to the backbone. To find these categories, have a brainstorming session with your team. The number of categories you create will vary according to your industry and the problem you’re solving. As an example, if you work in manufacturing, your major cause categories may be staff/people, equipment and machinery, processes and procedures, materials, environmental factors, and measuring procedures.

3. Brainstorm causes. 

Now that you have your major cause categories in place, take time to brainstorm possible causes. You can use the categories as a way of generating ideas or just list as many causes as you can think of as a team.

4. Categorize causes. 

Go through your list of causes and add them to the appropriate category on your diagram. These causes become the ribs on your diagram, joining categories to the backbone. 

5. Discover sub-causes. 

For each cause you identify, go deeper by asking effective questions such as, “Why does this happen?” This causes layers of branches or “bones” on the diagram. 

6. Identify root causes. 

The final step is to identify the root causes of the effect or problem in the problem statement. To do this, look at the causes that appear most often and across more than one category.

4 common types of fishbone diagrams

Fishbone diagrams come in various types, each designed to address a specific challenge. Here are some of the commonly used fishbone diagrams:

1. Simple fishbone diagram: The most frequently used fishbone diagram, the simple fishbone, lets you define and create cause categories unique to your organization or industry. With no predetermined category of causes, the simple fishbone diagram is the most versatile. For instance, when analyzing negative customer feedback, you might categorize causes as product-related and service-related concerns.

2. 4S fishbone diagram: The 4S fishbone diagram, widely used in the service industry, categorizes potential causes into four sections, each starting with the letter ‘S’, namely, surroundings, systems, skills, and suppliers:

  • Surroundings include the external environment of your business, such as customers.

  • Systems represent the essential internal processes for customer service or product delivery.

  • Skills denote competencies necessary for effective job performance, while suppliers involve employees, contractors, and partners collaborating on company projects.

3. 8P fishbone diagram: The 8P fishbone diagram features eight causes sections, each beginning with the letter ‘P’, which are procedures, policies, place, products, people, procedures, price, and promotion:

  • Procedures encompass what is needed for your company to operate.

  • Policies detail the rules and regulations set by your company.

  • Place indicates where your company operates from.

  • Product denotes what type of products your company will sell.

  • People refer to those working for you.

  • Processes describe how tasks are accomplished within your organization.

  • Price determines how much you should charge for your products and services.

  • Promotion outlines annual promotional activities.

While its primary use is in the service industry, this variation is adaptable for application in nearly all types of businesses and industries.

4. 6M fishbone diagram: This specific fishbone diagram is predominantly used in manufacturing. It categorizes potential problem causes into six attributes:

  • Man/manpower, encompassing employers and employees involved in designing and delivering a product

  • Method, which includes the production process, among other procedures contributing to the final product's delivery

  • Machine, referring to any systems or tools utilized in manufacturing

  • Material, denoting the raw materials and components necessary for creating the end product

  • Measurements, detailing the physical metrics of a product or work unit

  • Mother nature, which encompasses internal and environmental factors. 

Related terms

Read more: Project Management Terms: A to Z Glossary

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