Fishbone Diagrams in Quality Management: A Beginner’s Guide to Root Cause Analysis
Jun 7
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In the world of quality management, simply fixing surface-level problems isn’t enough. To truly solve issues and prevent them from recurring, we must identify their root causes—and that’s where the Fishbone Diagram, also known as the Ishikawa Diagram or Cause-and-Effect Diagram, becomes an essential tool.
This beginner-friendly guide will walk you through what Fishbone Diagrams are, how they work, and why they’re vital for driving continuous improvement.
🔍 What Is a Fishbone Diagram?
The Fishbone Diagram was developed in the 1960s by Kaoru Ishikawa, a pioneer in quality management. It gets its name from its shape, which resembles a fish skeleton. The “head” of the diagram shows the problem or effect, and the “bones” branching off represent major categories of causes.
The goal? To systematically uncover all possible root causes of a problem by organizing them into structured categories for analysis.
🧱 Components of a Fishbone Diagram
Effect (Problem Statement)
Clearly define the problem you're solving (e.g., "High customer complaints").
This goes at the “head” of the fish.
Main Cause Categories: Depending on your industry, you’ll use either:
6Ms (for manufacturing): Manpower, Methods, Machines, Materials, Measurements, and Environment
4Ps (for services): People, Policies, Procedures, Place
Sub-causes
These are specific issues under each category (e.g., "Insufficient training" under People).
Root Cause Identification
Use tools like the 5 Whys to explore sub-causes further and pinpoint the root of the issue.
🪛 How to Create a Fishbone Diagram (Step-by-Step)
To create a basic fishbone diagram, you will need something large to write on, like a flipchart or whiteboard. You also will need a group of individuals who possess the necessary knowledge about the area being analyzed.
Agree on the problem statement or effect being analyzed. For example, determining why there have been frequent defects in a series of pumps delivered to a customer.
Draw a horizontal, right-facing arrow in the center of the page—this will be the fish’s spine. At the end of the arrow, like the fish’s head, write the problem statement (e.g., frequent pump defects) and draw a box around it.
Identify the main categories of the problem’s causes and draw these as branches emanating from the central arrow, like a fish’s ribs. Ishikawa introduced the “6 M’s” as generic labels to describe the core categories, but he also encouraged creativity in naming these categories to communicate more clearly to those who would be using the diagram. The 6M’s stand for:
Materials—parts, ingredients, supplies
Machinery —production-related equipment, materials handling equipment, software (this may need to be a separate category for some industries/organizations)
Methods —procedures, techniques, processes, regulations (this may need to be a separate category for government and heavily regulated industries)
Measurement—key indicators, measurement devices, key data capture or collection points
Manpower—people and human resources, with their associated training, skills, competences
Mother Nature —environment and externalities
Less commonly included but useful for contemporary diagrams is a seventh M: Money —operating expenses and capital investments
Using the main categories as a guide, ask "Why does this happen?" to help brainstorm all possible causes of the problem, aiming for brief and succinct descriptions. As each idea is given, the facilitator writes it as a branch from the appropriate category. Causes can be written in several places if they relate to several categories.
Continue asking "Why?" to generate deeper levels of causes, writing subcauses as branches off the causes. Layers of branches indicate causal relationships.
When the group runs out of ideas, focus on the places where there are fewer ideas.
Analyze the identified causes to determine those that should be addressed further. Remember that the purpose is to cure the problem, not the symptoms. It may be necessary to redraw the fishbone diagram after the first version has been completed to keep things clear and organized for analysis.
If needed, follow up with additional tools like a responsibility matrix, which identifies who has ownership over the cause as well as how much control that person has over eliminating or reducing the effects of the cause.
Start creating your own fishbone diagram using this complimentary downloadable template as a guide for your larger-scale diagram.
🧪 Real-World Example: Late Delivery in an E-commerce Company
🟩 Problem: “Orders are being delivered 3+ days late to customers.”
Categories Explored:
People: Staff missed handoff deadlines, miscommunication
Processes: No standard operating procedure for rush orders
Technology: Glitches in order tracking system
Vendors: 3rd party courier inconsistencies
Inventory: Products out of stock, causing fulfillment delays
Policies: No escalation process for time-sensitive shipments
After plotting the Fishbone Diagram and analyzing each branch, the team discovered that:
Most delays occurred due to lack of a standardized rush order process.
This insight led to a cross-functional project to:
Define rush order criteria
Train staff on escalation procedures
Add alerts in the order tracking system
Result: Average delivery time improved by 40% in just one month.
🎯 Why Beginners Should Master the Fishbone Diagram
Here are key benefits of using this tool, especially for those new to Six Sigma or Lean:
Visual Clarity: Breaks down complex problems into manageable parts
Team Collaboration: Encourages diverse perspectives
Structured Thinking: Promotes disciplined analysis
Proactive Quality Management: Identifies problems before they escalate
It's also useful in a wide variety of industries—from manufacturing and healthcare to software development and service delivery.
⚠️ Common Challenges (and How to Overcome Them)
Too many causes: Focus on one problem at a time
No prioritization: Use a Pareto Chart or FMEA to rank impact
Subjectivity: Involve data and cross-functional teams to stay objective
✅ Final Thoughts
The Fishbone Diagram is more than just a visual tool—it’s a mindset for continuous improvement. Whether you're in a call center, hospital, factory, or tech company, this diagram helps you solve the real problem, not just treat the symptoms.
Start using Fishbone Diagrams today to uncover insights, engage your team, and build better processes that last.
📚 Citation
Fishbone Diagrams in Quality Management: How They Drive Improvements
By Project Management, LinkedIn | Jan 8, 2025
Fishbone, By ASQ, https://asq.org/quality-resources/fishbone
Image Source: ASQ