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Ishikawa Diagram

What Is an Ishikawa Diagram?

An Ishikawa diagram, also known as a fishbone diagram or cause-and-effect diagram, is a visual tool used to identify and organize the potential causes of a problem or an effect. It was developed by Kaoru Ishikawa, a Japanese quality control expert, in the 1960s.

The diagram takes its name from its appearance, as it resembles the shape of a fish skeleton. It consists of a horizontal line (the "spine") representing the problem or effect being investigated. Branching off from the spine are several diagonal lines (the "bones") that represent different categories of potential causes.

How Are Ishikawa Diagrams Used In Six Sigma?

Ishikawa diagrams are widely used in the Six Sigma methodology as a tool for problem-solving and root cause analysis. They help teams identify and understand the various factors that contribute to a problem or effect, allowing them to focus on addressing the root causes rather than just the symptoms.

By using Ishikawa diagrams in Six Sigma, teams can visually represent the complex relationships between causes and effects, leading to a better understanding of the problem and more effective solutions. The structured approach promotes collaboration, data-driven decision-making, and continuous improvement.

Understanding Ishikawa Diagrams

To understand an Ishikawa diagram effectively, you need to grasp the following key elements:

1. Clearly identify and understand the problem or effect that the Ishikawa diagram aims to address.

2. Understand the categories or factors under which potential causes are grouped. Familiarize yourself with the chosen categories and their relevance to the problem at hand.

3. Comprehend the potential causes listed under each category. Analyze and evaluate each cause to determine its relationship to the problem.

4. Grasp the cause-and-effect relationships depicted in the Ishikawa diagram. Understand that the branches and sub-branches of the diagram illustrate how different causes can contribute to the problem.

5. Understand the visual representation of the Ishikawa diagram. The central spine, diagonal branches, and cause branches create a visual structure that helps organize and communicate the causes and their relationships effectively.

By understanding these elements, you can effectively interpret and analyze an Ishikawa diagram, gaining insights into the causes contributing to a problem and guiding subsequent problem-solving efforts.

How to Make an Ishikawa Diagram

Here's how to develop and make an Ishikawa diagram:

Start with the Problem or Effect

Begin by clearly defining the problem or effect you want to investigate. This becomes the central "spine" of the diagram, drawn as a horizontal line. This is then entered in the “head” of the fish.

Identify Major Categories

Determine the major categories of potential causes related to the problem. Commonly used categories are the 6Ms: Manpower, Methods, Machines, Materials, Measurements, and Mother Nature. You can modify these categories based on your specific context.

Draw the Bones

From the main spine, draw diagonal lines (bones) extending outwards to represent each category. These lines should be spaced evenly, allowing enough room for listing the causes.

Brainstorm Causes

In a team setting, brainstorm all possible causes within each category. Encourage diverse perspectives and ideas. Write each cause as a branch off the respective category line.

Analyze Causes

Analyze each cause to understand its relationship to the problem. Ask "Why?" multiple times to dig deeper and uncover the underlying factors. This helps in identifying the root causes.

Subdivide Causes (if necessary)

If a cause is complex or can be further broken down, create sub-branches to represent the contributing factors. This hierarchical structure provides a more detailed analysis.

Validate Causes

Validate the potential causes using data, evidence, or expert knowledge. Ensure that the causes are based on facts rather than assumptions or biases.

Use Additional Tools

Complement the Ishikawa diagram with other problem-solving tools, such as data analysis, Pareto charts, or process maps, to gain a comprehensive understanding of the problem and its causes.

Take Action

Based on the analysis and validation, develop an action plan to address the identified root causes. Implement the necessary changes and monitor the results.

When to Use an Ishikawa Diagram

Here are some scenarios where you can effectively use an Ishikawa diagram:

  1. Problem analysis

  2. Root cause analysis

  3. Process improvement

  4. Quality management

  5. Team collaboration

  6. Decision-making

  7. Project planning

Types of Ishikawa Diagrams

While the classic 6M Ishikawa diagram is the most commonly used type, there are a few variations that can be employed depending on the specific requirements of the problem at hand. Here are a few types of Ishikawa diagrams:

  1. 4S Diagram

  2. 8P Diagram

  3. 3M Diagram

What are the 6Ms in the Ishikawa Diagram?

The 6Ms, often represented in an Ishikawa diagram, are the six major categories of potential causes that can contribute to a problem or effect. They serve as a framework for organizing and analyzing the causes. The 6Ms are:

  1. Manpower (People): This category refers to the human resources involved in the process or system. The word People is often substituted to be more politically correct.

  2. Methods: The methods category encompasses the processes, procedures, and techniques used to perform tasks or deliver products or services.

  3. Machines (Equipment): The machines category involves the equipment, tools, and machinery used in the process or system. The word Equipment is often substituted to reflect the use of an Ishikawa diagram in a non-manufacturing setting.

  4. Materials: The materials category includes all the physical inputs used in the process or system.

  5. Measurements: The measurements category relates to the data and metrics used to monitor and assess the process or system.

  6. Mother Nature (Environment): This category encompasses the external factors that are beyond human control and influence. It includes factors such as weather conditions, geographical location, natural disasters, regulatory requirements, and other environmental aspects that can impact the process or system.

What Does A Ishikawa Diagram Look Like?

An Ishikawa diagram has a distinct appearance that resembles the skeleton of a fish. Here is what a typical Ishikawa diagram looks like:

  1. Central Spine: The diagram starts with a horizontal line or spine drawn on a piece of paper, whiteboard, or digital tool. This line represents the problem or effect that you want to investigate. It is usually positioned on the right side of the diagram.

  2. Category Lines (Bones): Extending from the central spine, several diagonal lines branch out towards the left side of the diagram. These diagonal lines resemble the bones of a fish and represent the major categories of potential causes. The categories are typically labeled along these lines.

  3. Cause Branches: Under each category line, individual branches or lines extend outwards, forming smaller branches. These branches represent the specific potential causes related to the category. Causes are written as concise statements on the branches.

  4. Sub-branches (Optional): If a cause can be further broken down into sub-causes or contributing factors, additional branches can be created under the main cause branch. This hierarchical structure provides a more detailed analysis and understanding of the causes.

  5. Relationships: The Ishikawa diagram illustrates the cause-and-effect relationships between the problem or effect and the identified causes. The branches and sub-branches demonstrate how different factors contribute to the problem, helping to identify the root causes.

  6. Visual Representation: The diagram provides a visual representation of the causes and their relationships. It is usually hand-drawn or created using digital tools. The use of different colors or markers for the categories and causes can enhance the visual clarity and organization of the diagram.

Below is a graphical representation of an Ishikawa Diagram:

Two Hypothetical Examples

Here are two hypothetical examples of Ishikawa diagrams:

Example 1

Delayed Product Delivery Problem: The delivery of products to customers is frequently delayed.


  1. Manpower

  2. Methods

  3. Machines

  4. Materials

  5. Measurements

  6. Mother Nature (Environment)


  1. Manpower: Insufficient staffing levels, lack of training, ineffective communication.

  2. Methods: Inefficient scheduling, poor coordination between departments, inadequate prioritization.

  3. Machines: Equipment breakdowns, unreliable transportation vehicles, outdated technology.

  4. Materials: Shortage of raw materials, poor quality materials, delays in supplier deliveries.

  5. Measurements: Inaccurate tracking of inventory, inadequate performance metrics, lack of real-time monitoring.

  6. Mother Nature (Environment): Severe weather conditions, traffic congestion, natural disasters impacting transportation.

Example 2

High Error Rate in Data Entry Problem: There is a high error rate in data entry tasks.


  1. Manpower

  2. Methods

  3. Machines

  4. Materials

  5. Measurements

  6. Mother Nature (Environment)


  1. Manpower: Inadequate training, fatigue, lack of attention to detail.

  2. Methods: Unclear instructions, absence of standardized procedures, insufficient quality checks.

  3. Machines: Faulty keyboards or input devices, outdated software, hardware malfunctions.

  4. Materials: Illegible source documents, incomplete or inaccurate information provided.

  5. Measurements: Inadequate error tracking, lack of feedback mechanisms, absence of performance targets.

  6. Mother Nature (Environment): Poor lighting conditions, excessive noise, distractions impacting concentration.

The 6 M's Ishikawa Diagram

The 6 M's Ishikawa Diagram is a variation of the traditional Ishikawa diagram that focuses specifically on six major categories of potential causes. Here's an example of a 6 M's Ishikawa Diagram:

Problem: High defect rate in manufactured products.


  1. Manpower

  2. Methods

  3. Machines

  4. Materials

  5. Measurements

  6. Mother Nature (Environment)


1. Manpower:

○ Insufficient training on quality standards

○ Inadequate staffing levels

○ Lack of skills or expertise

2. Methods:

○ Ineffective quality control procedures

○ Inconsistent work instructions

○ Poor process documentation

3. Machines:

○ Equipment malfunctions or breakdowns

○ Inadequate maintenance practices

○ Outdated or inefficient machinery

4. Materials:

○ Low-quality raw materials

○ Inconsistent supply chain

○ Improper handling or storage of materials

5. Measurements:

○ Inaccurate measurement tools

○ Insufficient data collection methods

○ Lack of real-time monitoring

6. Mother Nature (Environment):

○ Temperature or humidity fluctuations

○ Power outages or electrical disturbances

○ Environmental contaminants affecting production

The 3 M's Ishikawa Diagram

A simple variation to the 6 M's Ishikawa diagram is the 3 M's diagram. In this variation, only man, machine, and materials are used. This may be more commonly seen in manufacturing processes that may experience less interaction with mother nature or processes that do not need constant measuring or refinement.

The 8 P's Ishikawa Diagram

The 8 P's Ishikawa Diagram is a variation of the traditional Ishikawa diagram that expands the categories to include eight major factors that can contribute to a problem or effect. The eight categories are::

  1. Product

  2. Price

  3. Place

  4. Promotion

  5. People

  6. Processes/Policies

  7. Physical Evidence

  8. Packaging

The 8 P's Ishikawa Diagram expands the categories to cover various aspects of the business, allowing for a more comprehensive analysis of the potential causes. The 8 P's model is commonly used in marketing and service-related industries, where the factors play a significant role in customer satisfaction and experience.

The 4 S's Ishikawa Diagram

The 4 S's Ishikawa Diagram is a variation of the traditional Ishikawa diagram that focuses on four major categories starting with the letter 'S.' They are:

  1. Surroundings

  2. Suppliers

  3. Systems

  4. Skills

What Is an Ishikawa Diagram Used for?

. Here are some common uses of Ishikawa diagrams:

● Ishikawa diagrams are extensively used in problem-solving processes. They help identify and organize potential causes contributing to a problem or effect.

● Ishikawa diagrams are effective in conducting root cause analysis. They provide a structured approach to identifying the underlying factors leading to a problem.

● Ishikawa diagrams are widely used in quality management initiatives such as Total Quality Management (TQM) and Six Sigma. They assist in quality improvement efforts by identifying the causes of defects, errors, or quality issues.

● Ishikawa diagrams are helpful in analyzing and improving processes. They allow teams to identify the factors that influence process performance and identify areas for improvement.

● Ishikawa diagrams promote collaboration among team members. The visual nature of the diagram enhances communication and facilitates shared understanding among team members.

● Ishikawa diagrams can aid in decision-making processes. The diagram helps in identifying the most significant causes and guiding effective decision-making.

Why Is It Called an Ishikawa Diagram?

An Ishikawa diagram is named after its creator, Kaoru Ishikawa, a renowned Japanese quality control expert and professor at the University of Tokyo. In the 1960s, Ishikawa developed the diagram as a visual tool to analyze and understand the causes contributing to a problem or effect. Given Ishikawa's significant role in developing the diagram and his influence in quality management practices, the diagram became widely known as the "Ishikawa diagram" or "Ishikawa fishbone diagram." The term "fishbone diagram" stems from the diagram's resemblance to a fish skeleton, with the central spine representing the problem and the branching lines representing the causes.

This is not to be confused with the Noto Peninsula which is a peninsula that projects north into the Sea of Japan from the coast of Ishikawa Prefecture in central Honshū, the main island of Japan.

Advantages and Disadvantages of an Ishikawa Diagram

Ishikawa diagrams offer several advantages and disadvantages. Here are some of the key advantages:

  1. Visual representation

  2. Systematic approach

  3. Identifying root causes

  4. Collaboration and brainstorming

  5. Decision support

Despite these advantages, there are a few potential disadvantages to consider:

  1. Possible over-simplification

  2. Can rely too much on subjectivity

  3. Lack of quantitative analysis

  4. Time and effort

To mitigate these disadvantages, it is essential to use Ishikawa diagrams in conjunction with other problem-solving tools, data analysis, and expert knowledge. They should be seen as one component of a comprehensive problem-solving and analysis process rather than the sole method of analysis.

How To Learn More About Ishikawa Diagrams

To learn more about Ishikawa diagrams, there are several resources and approaches you can explore:

● There are numerous books and publications available that delve into the concept, applications, and practical use of Ishikawa diagrams. Some recommended books include "Introduction to Quality Control" by Kaoru Ishikawa and "The Quality Toolbox" by Nancy R. Tague.

● Many online platforms offer courses and tutorials on quality management and problem-solving methodologies that cover Ishikawa diagrams. Websites like Udemy, Coursera, YouTube,,, and LinkedIn Learning provide a range of courses, articles and videos taught by industry experts.

● Explore resources provided by quality management organizations such as the American Society for Quality (ASQ), the International Organization for Standardization (ISO), or the Six Sigma Institute. These organizations often offer training materials, webinars, and publications related to Ishikawa diagrams.

● Studying real-world case studies and examples can enhance your understanding of how Ishikawa diagrams are applied in different industries and problem-solving scenarios. Look for case studies in quality management books or publications or search for relevant examples online.

● The best way to learn about Ishikawa diagrams is to practice creating them and applying them to real or hypothetical problems. Start by identifying a problem or effect, create an Ishikawa diagram to analyze the potential causes, and validate the causes through data analysis or expert input.

● Engage with professionals in the field of quality management, problem-solving, or process improvement. Attend industry conferences, seminars, or webinars to network and learn from experts who have experience with Ishikawa diagrams.

How To Get Certified In Lean Six Sigma

To get certified in Lean Six Sigma, you can follow these general steps:

Sign up with an IASSC accredited organization like

★ Lean Six Sigma certifications are available at different levels, such as Yellow Belt, Green Belt, Black Belt, and Master Black Belt. Decide which level aligns with your experience, role, and career goals.

★ Research different certification bodies that offer Lean Six Sigma certifications. Some well-known organizations include the American Society for Quality (ASQ), International Association for Six Sigma Certification (IASSC),, and Lean Six Sigma Institute (LSSI).

★ Once you've chosen a certification body, explore their certification programs and requirements. Each body may have different criteria, training options, and exam formats.

★ Enroll in a Lean Six Sigma training program that aligns with your chosen certification level. Training options can include classroom-based training, online courses, or a combination of both.

★ Dedicate time to study the Lean Six Sigma methodologies, tools, and concepts covered in the training program. Review course materials, textbooks, and recommended resources. Practice applying Lean Six Sigma principles to real-world scenarios and problem-solving situations.

★ After completing the training, you will need to pass a certification exam to earn your Lean Six Sigma certification. The exam format and passing criteria will vary depending on the certification body.

★ Some certification programs may have a practical experience requirement, where you need to apply Lean Six Sigma principles and complete a project within your organization or complete a simulation.

★ Submit Certification Application: Complete the certification application process, which may include submitting your exam results, project documentation (if applicable), and other required information. Pay any applicable certification fees.

Frequently Asked Questions About an Ishikawa Diagram

What is the difference between a fishbone and an Ishikawa Diagram?

There is no fundamental difference between a fishbone diagram and an Ishikawa diagram. In fact, the terms "fishbone diagram" and "Ishikawa diagram" are often used interchangeably to refer to the same type of diagram.

The fishbone diagram is so named because of its visual resemblance to a fish skeleton, with the problem or effect represented as the fish's head and the causes represented as the bones branching out from the spine. The term "Ishikawa diagram" is derived from its creator, Kaoru Ishikawa, a quality control expert who popularized the use of this diagram in problem-solving and quality management.

What is the difference between brainstorming and Ishikawa Diagram?

Brainstorming is a technique used to generate ideas and possibilities, while Ishikawa Diagrams are tools used to analyze and categorize the causes contributing to a problem. Brainstorming is more focused on creative idea generation, while Ishikawa Diagrams provide a visual framework for cause-and-effect analysis. Both techniques can be used in conjunction to facilitate problem-solving and generate potential solutions.

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