What is a Fishbone Diagram? (or Ishikawa Diagram)

A Fishbone Diagram template (also known as a cause-and-effect diagram or Ishikawa Diagram) is an important LEAN tool that can be used in excel to help brainstorm, identify potential causes, and sort ideas into useful categories. A fishbone diagram can be used to visually see cause and effect. This method is more structured than other tools for brainstorming the causes of a problem, such as the Five Whys tool. The head or mouth of the fish displays the problem or effect. The smaller “bones”, which are part of the various cause categories, list possible contributing causes. A fishbone diagram is a useful tool for identifying the potential causes of a problem. It allows the team to examine the distinct categories and consider alternative causes. Team members with personal knowledge of the systems and processes involved in the event or problem should be included.

Kaoru Ishikawa, who was trying to solve problems at Kawasaki shipyards during the 1960s, revived the fishbone diagram idea and it quickly became popular. The fishbone diagram was not new even in the 1960s. It was used as a quality control tool in the 1920s.

To overcome the problems identified in a fishbone diagram, the Mazda Miata car is a classic. It was even possible to design the doors of the Mazda Miata so that the driver could rest their arm on them while driving.

Variation is the enemy

Variation is your enemy when it comes to quality or efficiency. No matter what your business is, it’s important to not leave anything to chance. A predictable process should begin from the moment your client contacts us. The goal is customer satisfaction. Variation in the process can lead to variation in the product.

Fishbone diagrams can help you identify the variables that could be involved in the equation. These diagrams allow you to plan your projects so you can deal with them in a way that ensures that your final product meets your expectations.

Categorizing Variation Sources

Although there are many potential causes for variation, they all fall within the following categories:

  • Methodologies – Here you will see the importance of policies, rules, regulations, or procedures to maintain consistent quality.
  • People – You can find ways to make sure that everyone involved in a project knows what to do and when.
  • Measurements – How are the measurements and monitoring done to determine quality?
  • Environment – This refers to anything that is not under the control of the company and may have an impact on the results.
  • Machinery – This could include anything from robots for assembly lines to tools, or computers.
  • Materials – It is important to consider the materials that are required for a high-quality product.

These six categories can be used to create your fishbone diagram. You can indicate sub-factors by attaching mini-fish bones to the line.

The 5 Ms for identifying causes of variation in manufacturing

There are many ways to choose the most important categories that will affect your quality. Toyota created the 5Ms list as a list. Later thought leaders added 3 more Ms to it for a total 8. These are:

  • Man
  • Material
  • Machine
  • Method
  • Measure

Troubleshooting Service Industry Problems

What happens if your company does not produce physical products? Use the 5S method in this instance.

  • Suppliers
  • Surroundings
  • Systems
  • There are many skills available
  • Documentation standard

Drawing the Backbone

The head of the fish represents the “Effect” (or the Problem in which we are trying to find the root cause). The bones coming off the main backbone are high-level “Causes” that branch off to sub-causes and potentially to root causes.

  • Create the head of the fishbone diagram template in excel which lists the problem or issue to be investigated. Be specific about how and when the problem occurs.
  • Create a backbone for the fish (a straight line that leads to the head).
fishbone diagram
Fishbone diagram with example; Template for fishbone diagram

Drawing the Main Bones (the Main Causes)

In the “Fishbone Diagram” or “Ishikawa Diagram”, we draw the main bones that come off the backbone. There are two separate ways we can categorize these bones:

  • These bones could be the main causes of the effect (or problem) which we can drill down further to discover root causes, or
  • We can use generic categorizations (like the ones below)
    • Methods (for example, SOP’s, work instructions, OJT)
    • Machines (or equipment, databases, IT assets)
    • People (labor or manpower)
    • Materials (actual materials or information)
    • Measurement (for example KPI’s, exception reports, production expectancies)
    • Environment (for example noise, temperature, culture)
fishbone diagram
Fishbone diagram with example; Template for fishbone diagram

The Contributing Causes

From the main bones we now dig deeper in the “Fishbone Diagram” or “Ishikawa Diagram” into the potential contributing causes.

fishbone diagram
Fishbone diagram with example; Template for fishbone diagram

We then ask “Why”

We keep asking “Why do the contributing cause happen?” to dig deeper in the potential root causes.

fishbone diagram
Fishbone diagram with example; Template for fishbone diagram

Actionable Root Causes

It is especially important in the “Fishbone Diagram” or “Ishikawa Diagram” that the potential root causes are ACTIONABLE ITEMS! Actionable items are problems that we can implement a tangible fix. For example, one of the root causes of the effect of “Employees are an average of 7 minutes late to work over a 30-day period” is that the metric of “on-time” has not been defined in the employee handbook. The fix to this is tangible (to define “on time” and subsequently to measure timeliness).

What did you think?

Did this article help you and your team to develop an effective Fishbone Diagram template in excel? Please share your thoughts in the comments below.