Mastering Root Cause Analysis: Unveiling the Power of the Fishbone Diagram

Fishbone diagram , also known as cause and effect diagram or Ishikawa diagram is a quality management tool that is commonly used to identify the root cause of a problem. Basically, it analyzes various possible causes of a problem with the help of brainstorming sessions. In this article, we will review the Fishbone diagram (cause and effect diagram or Ishikawa diagram ) as a problem solving tool and discuss the advantages and limitations of it.

The concept of the Fishbone Diagram was developed by a Japanese Professor, Dr. Kaoru Ishikawa in the 1960s. This diagram looks like a fish skeleton so that it took its name from its appearance. It is also named as “Ishikawa Diagram”.

It is a visual quality management tool that provides an overall list of possible causes to determine the root cause of a specific event. Each defect or cause is a source of variation. It helps to understand what causes a problem and what are the possible ways to solve it.

The Fishbone Diagram (Cause and Effect Diagram or Ishikawa Diagram) is one of the seven basic tools of quality.

What are the Seven Basic Quality Tools ?

The seven basic quality tools are graphing techniques that people commonly use for quality control management purposes. They are easy to use and implement.

1. Fishbone Diagram (Cause and Effect Diagram or Ishikawa Diagram)
2. Check sheet
3. Control chart
4. Histogram
5. Pareto chart
6. Scatter diagram
7. Stratification

Categorization of Causes

Fishbone (cause and effect diagram or Ishikawa diagram ) diagrams are commonly used in many industries such as service, manufacturing, marketing, and construction. Causes of problems may arise from typical categories based on the industry. Below are a few suggested categories for some industries. They may be helpful to create the framework.

Service Industries

In the service industry, you can categorize the factors (causes) by 4Ps:
• Policies
• Plant/Technology
• Procedures
• People

Manufacturing Industries

In the Manufacturing industry, you can categorize the factors (causes) by 6Ms:
• Material
• Manpower
• Measurement
• Mother Nature (Environment)
• Management
• Machine

Marketing Industries

In the Marketing industry, you can categorize the factors (causes) by 7Ps:
• Place
• Promotion
• People
• Packaging
• Product
• Price
• Positioning

Many classifications can be made for categorization of causes in a fishbone diagram ; however, the above are more popular than the others.

How to Create a Fishbone Diagram (Cause and Effect Diagram or Ishikawa Diagram)?

Below steps can be followed to create a fishbone diagram for problem solving.

1. Identify the Problem (Effect)

Once all the project team agreed on the problem, the problem expression can be written in a box at the mouth of the fish.

2. Define the major categories of causes for the Problem

Major categories can be defined by the help of brainstorming sessions. Then, the major categories can be written as branches from the main arrow. Major categories often include Material, Manpower, People, etc.

3. Brainstorm all the possible causes

In this step, brainstorming can be made by group/team members based on their prior experiences. During brainstorming, ask “Why does this happen?” Then note the answer.

Write the causes horizontally to the fishbone where they belong. If the causes are related to various categories, you can write them in several places.

Then, ask again “Why does this happen?” for each cause. Write sub-causes branching off the cause branches.

Note that the 5 whys technique is often used in conjunction with the fishbone  – keep asking why until you get to the root cause.

4. Analyze the Fishbone Diagram

Once the fishbone is completed, an investigation can be made with team members to identify the root cause of the problem. The solution can be determined and corrective actions can be taken.

Benefits of Fishbone Diagram (Cause and Effect Diagram or Ishikawa Diagram)

Below are a few benefits of this diagram (Cause and Effect Diagram or Ishikawa Diagram).

The Fishbone Diagram;

• It is a visual tool which displays the links and relationships among the potential causes and results displayed in the diagram.
• Demonstrates all causes simultaneously.
• Encourages brainstorming about the reasons for a certain result because it captures all the causes.
• Stimulates your team to explore the root cause of a problem.
• Improves decision making within the project team.
• Helps to determine the methods to improve the process and take corrective actions.

Limitations/Drawbacks of Fishbone Diagram

Below are some of the limitations of this quality management tool (Cause and Effect Diagram or Ishikawa Diagram).

• For a realistic result, a skilled team is required to make brainstorming.
• In complex situations, it is difficult to represent the interrelated nature of problems and causes.
• Sometimes it can be hard to determine the root cause of a problem because of the team members bias.

Summary

The fishbone diagram is a powerful process improvement technique which greatly helps to determine the important factors involved in a process. It is one of the seven basic tools of quality widely used for problem-solving. In order to use this technique, create a team and agree on the problem. Then, define the categories of causes related to the problem and start brainstorming sessions. Brainstorming provides different point o views that you can take advantage of team members experiences. 5 Whys technique can be used during brainstorming sessions. Creating this diagram encourages teamwork and builds trust between departments. It is widely used in many industries such as construction, healthcare, medical, etc. as a problem-solving tool.

Are you using fishbone diagrams for problem solving in your projects? If you are, please share your experiences regarding how you use them.

External References

[1] American Society for Quality

Tags: Benefits of a Fishbone Diagram Cause-and-effect diagram Fishbone Diagram How to Create a Fishbone Diagram Ishikawa Diagram Limitations/Drawbacks of a Fishbone Diagram