How to Create an Ishikawa Diagram for Problem Solving

The Ishikawa diagram is a graphical tool that helps you to identify all of the potential causes of a problem or issue. It is also sometimes known as the fishbone diagram or cause and effect diagram. The Ishikawa diagram was popularized in the 1960s by Kaoru Ishikawa Kaoru Ishikawa, who developed quality management processes for `the Kawasaki shipyards.
An Ishikawa or Fishbone diagram using the manufacturing categories: man, machine, method, environment, management

How to create an Ishikawa diagram

Creating an Ishikawa diagram is a simple process. First, you need to identify the problem or issue that you want to investigate. Then, you draw a large bone shape on a piece of paper or whiteboard. This will be the main ‘spine’ of your diagram.

Next, you need to identify all of the potential causes of the problem. These will be the ‘bones’ that branch off from the main spine. There are typically six main categories of causes:
  • People
  • Methods
  • Materials
  • Environment
  • Measurement
  • Management

People category

This could include training, skills, experience or knowledge. For example, if you are investigating a problem with a product that you manufacture, the people category would include the workers who make the product, as well as the designers and engineers who created it.

Methods category

This includes the processes and procedures that are used to make or do something. For example, if you are investigating a problem with a product that you manufacture, the methods category would include the steps in the manufacturing process.

Materials category

This includes the raw materials, parts and components that are used to make a product. For example, if you are investigating a problem with a product that you manufacture, the materials category would include the types of materials used to make the product.

Environment category

This includes the physical conditions under which something is made or done. For example, if you are investigating a problem with a product that you manufacture, the environment category would include the temperature and humidity of the factory, as well as the lighting conditions.

Measurement category

This includes the tools and methods that are used to measure something. For example, if you are investigating a problem with a product that you manufacture, the measurement category would include the gauges and instruments used to measure the dimensions of the product.

Management category

This includes the policies, decisions and actions of management. For example, if you are investigating a problem with a product that you manufacture, the management category would include the decisions that were made about the design of the product, as well as the production quotas that were set.

How to use the Fishbone diagram

Once you have identified all of the potential causes, you can start to investigate which ones are actually contributing to the problem. This is where the fishbone diagram comes into its own, as it provides a structure to help you systematically eliminate potential contributing factors until you identify the root cause of the problem.

Under each category add sub 'bones' for each activity, element, tool or person involved and think about what causes might be present. For example, let's say you need to reduce the time it takes to pay your suppliers invoices. Under people you would list everyone involved in the payment process and then establish if they contribute to the problem. In the example below, the buyer failure to create a purchase order and accounting's backlog delay payment, but supplier management don't seem to have an impact.
an example of a completed fishbone diagram to identify the causes of delays in paying invoices.

When to use it

The Ishikawa diagram is an extremely powerful tool for root cause analysis, and can be used in a wide variety of situations. Here are some examples:
  • When you need to identify the cause of a problem
  • When you need to improve a process or product
  • When you need to brainstorm ideas for a new product or service
  • When you need to make a decision about which solution to implement

When to avoid using it

The Ishikawa diagram is not always the best tool for the job. Here are some situations where it might not be the most appropriate:
  • When the problem is very simple and there is only one possible cause.
  • When you need to identify all potential causes of a problem (in which case, a brainstorming session might be more appropriate).
  • There could be many causes for complex defects, which can make the diagram cluttered. In this case you could use pareto analysis to identify the top 20% of causes for further analysis.
  • The relationships between different causes can be difficult to identify. Using a flow diagram may be more appropriate, particularly for processes that cross multiple teams or functions.

Top tips for getting the most out of Ishikawa diagrams

  • Keep it simple - don't try to include too many factors on your diagram. Remember, the aim is to help you focus on the most important causes of a problem.
  • Be specific - when you identify a cause, make sure it is as specific as possible. For example, rather than writing "lack of training", you could write "employees not receiving sufficient training on the new software".
  • Get input from others - Ishikawa diagrams are most effective when they're created by a team. So, if you're working on a problem with others, make sure to get their input.
  • Use color - using different colors for different categories of causes can help to make your diagram more visually appealing and easier to understand.

Combining Ishikawa with pareto analysis

Pareto analysis is a tool that can be used in conjunction with Ishikawa diagrams. Pareto analysis is based on the principle that 80% of problems are caused by 20% of causes. So, when you're looking at your diagram, try to identify the 20% of causes that are causing the majority of the problems. This will help you to focus your efforts on the most important causes.

Four variations of the fishbone diagram

Since the 1960s cause and effect diagrams have been used in many industries and verticals, and different versions tailored to particular situations have emerged.

The 5Ms used in manufacturing

This is the type we describe above: Method, Machines, Manpower, Materials and Measurement. It's used to study manufacturing and production processes. Three other categories can be added: Mission, Management and Maintenance.

The 8Ps used in product marketing

The 8Ps not surprisingly uses 8 spines: product, place, price, promotion, people, process, physical evidence and performance.

The 4Ss used in service industries

Surroundings, suppliers, systems and skill. Safety can also be added. This is similar to the 5Ms but tailored to service businesses.

Download the Ishikawa template

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