Jul 15, 2026

Fishbone Diagram and Its Purpose in Quality Analysis

Every business runs into quality problems at some point. It can be a process breakdown or a product failing inspection. While you can point to the most obvious, surface-level reason, there are often many factors that contribute to it. That's where a fishbone diagram comes in.

In this article, we cover what a fishbone diagram is, the different types, how to create one, and why it is a valuable tool for quality analysis.

What is a Fishbone Diagram?

A fishbone diagram, also termed an Ishikawa or cause-and-effect diagram, is a visual method for performing root cause analysis. It is a structured approach used by quality and operational managers to improve processes, reduce defects, and deliver consistent value to customers. It is one of the seven basic quality tools that help determine the root cause of a problem in quality management.

The name fishbone diagram comes from the resemblance of its shape to the skeleton of a fish. In a root cause analysis utilizing a fishbone diagram, a right-facing arrow is drawn. The problem would be written at the end of the arrow, called the fish head. The rest of the body is considered the fish spine, from which all possible categories of causes branch off.

It was developed by Kaoru Ishikawa at the University of Tokyo in the 1960s to measure quality control processes in the shipbuilding industry. Today, it is used across manufacturing, technology, financial services, healthcare, and the service industry.

Types of Fishbone Diagram

Every organization can determine their own set of categories for the fishbone diagram used in quality management. Below are some of the commonly used structures of a fishbone diagram.

1. 6M Fishbone Diagram

The 6M is the classic version of the fishbone diagram, which was introduced by Kaoru Ishikawa. It is mostly used in manufacturing industries and consists of the following categories:

Material
Machinery
Measurement
Manpower
Method
Mother Nature (Environment)

2. 4S Fishbone Diagram

The 4S fishbone diagram is used in the service industry and is beneficial when you want to involve the whole facility in problem-solving. Its components are:

Suppliers
Systems
Surroundings
Skills

3. 8P Fishbone Diagram

8P is yet another fishbone diagram used in the service industry and administrative function. Its categories are:

Place
People
Product
Procedure
Price
Policy
Process
Promotion

Procedure for Creating a Fishbone Diagram

By using a fishbone diagram, you can identify the root cause of your business problems and quickly implement corrective action to resolve them. To reap successful results, you should conduct a brainstorming session with different members in your organization and methodically approach the problem. Here’s a step-by-step guide for creating a fishbone diagram.

Procedure for Creating a Fishbone Diagram

Step 1 - Define the Problem

Start by clearly stating the problem you want to solve and write it at the right end of the diagram, where the fish head will go. Be very specific about the problem.

Step 2 - Identify Main Categories

Draw branches from the “fish spine”. Each branch would represent the category of causes behind the problem. In the commonly used 6M model, it would include material, machinery, measurement, manpower, method and mother nature (environment). You can use different categories that suit your situation.

Step 3 - Brainstorm Causes

For each category, ask, "What could be causing this problem here?" Write each cause as a smaller branch coming off the main category line. If a cause has sub-causes, branch those off further. Keep on asking "why" until you've gone as deep as you can.

Step 4 - Analyze the Diagram

Once all the causes are on the diagram, step back and look at the full picture.

Ask yourself:

Which causes appear most often?
Which ones are most likely to be driving the problem?
Which ones can you actually control or fix?

Circle the causes that seem most significant. These become your focus for corrective action.

Step 5 - Take Action

A fishbone diagram on its own doesn't solve anything. To implement an effective corrective action plan, you have to investigate the most likely root causes. Once identified, you can put a fix in place and monitor whether the problem improves.

What is the Purpose of a Fishbone Diagram in Quality Management?

For a quality manager, maintaining consistency in business processes, preventing defects, and improving customer satisfaction are their main concerns. This makes regular quality analysis a must.

Even ISO 9001, the international standard for quality management systems, emphasizes connecting customer requirements to your organization's objectives, engaging the workforce in quality management, and continually improving your processes with evidence-based decisions for corrective and preventive actions.

Being one of the seven quality tools, the fishbone diagram aligns with the goals of quality analysis with:

1. Root Cause Analysis

The main purpose of fishbone diagrams in quality management is to facilitate root cause analysis. By visualizing all potential causes of a problem in one place, it helps teams identify underlying factors affecting it and accordingly take corrective actions.

2. Structured Thinking

Fishbone diagrams promote structured thinking among team members during brainstorming sessions by sorting the causes of a problem into appropriate categories, and making them an evidence-based approach for improving quality and organizational processes.

3. Enhanced Team Collaboration

The input for different categories in a fishbone diagram doesn’t come from a single higher authority but from different personnel across the organization who are involved with the process that is currently facing issues and, subsequently, the causes behind it. To resolve the problem, all of them have to work in collaboration.

4. Better Decision-Making

As a fishbone diagram considers various factors that cause the problem and involves input from different members of the organisation, it significantly improves the decision on corrective actions, as you will be looking at various perspectives. This benefit will also reflect positively in your mitigation costs and resource allocation.

Wrapping Up

Quality problems rarely have a single, obvious cause. More often, they are the result of several things going wrong at once. Issues can stem from the people involved, equipment and materials used in production or some external factor. A fishbone diagram helps you see all of that clearly in one place.

Moreover, it aligns with ISO 9001 by bringing teams together, encouraging honest discussion, and making sure corrective actions are based on real evidence rather than assumptions.

If your goal is to obtain ISO 9001 certification for your quality management system, then Effivity’s cloud-based software is the one for you. Efffivity’s preconfigured, highly results-oriented QMS software automates your workflow. It lets you monitor all your business processes from one single platform, allowing you to make quick and informed decisions.

Book a free trial with Effivity to streamline your quality management system.

Shanker

Co-Founder & CEO at Effivity Technologies Pvt. Ltd.

Shanker brings over 20+ years of tech experience, including senior roles at Intel. At Effivity, he built the IT team from Scratch, managed budgets, and improved the product based on customer feedback. Shanker's leadership keeps Effivity at the forefront of the tech industry.

View All Posts

Improve Workflow & Profitability with Superior Integrated Management System Software free-demo

Schedule a Free Demo