Selecting and Customizing Fishbone Categories

At a recent software delivery review, a team spent two hours debating whether a deployment failure stemmed from “people” or “process” in their Fishbone diagram. The issue wasn’t the lack of effort—it was the category structure they’d blindly followed. I’ve seen this play out in manufacturing, healthcare, and service environments: rigid templates often obscure real causes. The truth is, fishbone categories are not one-size-fits-all. They’re tools to guide thinking—not boxes to fit problems into.

When used correctly, fishbone categories help teams structure their investigation, avoid bias, and uncover systemic issues. But misapplied, they become mental traps. In this chapter, I’ll walk you through how to choose or adapt categories based on your domain, using practical examples from real projects I’ve led. You’ll learn when to follow standard models like the 6M method fishbone and when to create custom fishbone branches that reflect your unique processes.

Understanding the Purpose of Fishbone Categories

Fishbone categories are not a rigid framework—they are cognitive scaffolds. Their primary function is to prevent premature closure by prompting diverse lines of inquiry. A well-chosen set of categories ensures you’re not missing hidden root causes buried in overlooked domains.

Without structured categories, teams often fall into pattern recognition bias—seeing only what fits their preconceptions. A category system forces exploration across multiple dimensions, increasing the odds of uncovering the true systemic failure.

Consider this: a failure in a hospital’s medication distribution process wasn’t due to “people” or “process” alone. It was because the IT system used a non-standard drug code that wasn’t flagged in the pharmacy’s master list—something that wouldn’t surface under a generic “people” or “technology” branch.

Why Standard Schemes Often Fall Short

Popular frameworks like the 6M (Man, Machine, Method, Measurement, Mother Nature, Management) or 4S (Surroundings, Suppliers, Systems, Skills) are helpful starting points. But they’re designed for manufacturing contexts and don’t always align with service or digital systems.

For example, in a logistics company, “Mother Nature” might include weather delays, but in a service desk environment, that same category becomes meaningless. Similarly, “Management” in a 6M diagram rarely captures the nuanced role of decision-making delays caused by approval workflows.

These mismatches don’t invalidate the models—they highlight the need for adaptation. The goal is not to follow a template, but to use its structure to explore all possible cause domains.

Popular Fishbone Category Schemes

Here’s a breakdown of the most widely used category schemes, with real-world strengths and limitations.

6M Method Fishbone

Originally developed for manufacturing, the 6M method includes:

• Man (People)
• Machine (Equipment)
• Method (Process)
• Measurement
• Material (Supplies)
• Management (Systems)

The 6M method fishbone works well when process steps are tangible and repeatable. In a steel mill, you can clearly separate “Machine” from “Method.” But in a call center, “Machine” becomes ambiguous—does it refer to the phone system, the CRM, or the headset?

My advice: use 6M only if your process involves physical assets and material flow. Otherwise, replace or rename branches to better reflect your operations.

4S Method Fishbone

Designed for service industries, this model includes:

• Surroundings (Environment)
• Suppliers (Input sources)
• Systems (Processes, IT tools)
• Skills (People capabilities)

The 4S method shines in service environments where inputs, people, and environment are central. For instance, in a bank’s loan processing unit, “Suppliers” can represent external credit bureaus, and “Surroundings” might include the IT infrastructure during peak load.

However, the 4S model omits “Measurement,” which can be a gap in data-driven processes. In a digital service team, validating success through KPIs is critical. You may need to add a “Measurement” branch or rename “Skills” to “People & Competence” for clarity.

8P Method Fishbone

Used in service and product delivery, the 8P model includes:

• Product
• Price
• Place
• People
• Process
• Physical Evidence
• Performance
• Productivity

This is especially powerful in marketing, retail, and customer experience teams. In a hospitality case study, “Physical Evidence” uncovered that guest check-in delays were caused by poorly labeled kiosks—something no other category would have flagged.

But in technical environments, “Price,” “Place,” and “Product” become irrelevant. I’ve adapted this model for IT service teams by replacing “Product” with “System” and “Performance” with “System Reliability,” while keeping “People” and “Process” intact.

How to Customize Fishbone Branches for Your Industry

Adapting fishbone categories isn’t about creative freedom—it’s about relevance. Start by analyzing your process’s core challenges.

Step-by-Step: Building Custom Fishbone Branches

1. Clarify the problem. What’s the effect? Be specific: “Customer refund request rate increased by 23% in Q1” not “We have issues with refunds.”
2. Map your process flow. Identify key touchpoints—people, systems, handoffs, decision points.
3. Group failure points. Categorize where breakdowns occur: system delays, handoff errors, data inconsistencies, etc.
4. Design branches based on actual risk domains. Use real pain points, not generic labels.
5. Validate with stakeholders. Ask team members: “Does this branch help us explore the real issues?”

For instance, in a healthcare setting, I replaced “Method” with “Clinical Workflow” and added “Regulatory Compliance” as a separate branch. The team realized that audit findings were not due to staff errors but outdated documentation protocols.

Examples of Custom Fishbone Branches by Sector

Industry	Standard Category	Customized Branches
IT/DevOps	Man, Machine, Method	Code Quality, CI/CD Pipeline, Environment Configuration, Dependency Management, Deployment Strategy
Healthcare	Man, Method, Measurement	Clinical Workflow, Medication Protocol, EHR Integration, Staff Training, Regulatory Compliance
Customer Service	People, Process, Technology	Agent Training, Response Time, Customer Journey Stage, CRM Functionality, Escalation Path
Manufacturing	6M	Machine Calibration, Raw Material Batch, Shift Handover, Safety Compliance, Maintenance Schedule

These aren’t replacements—they’re refinements. The goal is precision, not novelty.

Common Pitfalls and How to Avoid Them

Even with good intentions, teams make predictable mistakes when customizing fishbone categories.

1. Overloading or Under-Explaining Branches

Too many branches (e.g., 12+), and your team loses focus. Too few (e.g., 2–3), and you risk missing systemic causes.

Rule of thumb: 4–7 branches is optimal. If you need more, group them into subcategories (e.g., “Process” → “Order Entry,” “Approval,” “Shipping”).

2. Using Vague or Overlapping Labels

“People” and “Skills” are redundant. “Systems” and “Technology” overlap. Use distinct, non-overlapping labels.

Instead of “Management,” ask: “What decisions were delayed? Who approved what?” Then label the branch “Approval Process” or “Decision Delays.”

3. Ignoring the Context of the Problem

Applying the same category scheme to a software outage and a customer complaint is a recipe for irrelevance. Always align categories with the nature of the failure.

If the issue is data inaccuracy in a report, don’t start with “People.” Instead, ask: “Where does data originate? How is it validated? What systems transform it?” Use branches like “Data Source,” “Validation Rules,” “Transformation Logic.”

Best Practices for Fishbone Categories in Real Projects

Here’s what I’ve learned from over 30 root cause investigations across industries:

• Start with the problem, not the template. Your category system must reflect the failure, not the other way around.
• Use real process maps to guide categorization. A swimlane diagram reveals where handoffs occur—perfect for identifying branches.
• Let the team name the branches. When stakeholders co-create categories, they take ownership of the investigation.
• Revisit categories after the brainstorming phase. If causes keep clustering in one area, you may need to restructure.
• Document your rationale. When customizing, note why you removed or added a branch. This supports auditability and future reuse.

Frequently Asked Questions

How do I choose the right fishbone category scheme for my project?

Ask: What kind of process are we analyzing? If it’s manufacturing, 6M method fishbone works well. For services, 4S or 8P may be better. For IT, focus on system layers—code, deployment, integrations. Always let the problem define the structure, not the other way around.

Can I mix categories from different models?

Yes—this is encouraged. For example, use “People” from 6M, “Systems” from 4S, and “CI/CD Pipeline” from DevOps. The key is clarity and non-redundancy. Ensure each branch leads to distinct lines of inquiry.

How do I use fishbone for services when the issue isn’t process-related?

Service failures often stem from unstructured touchpoints. Use branches like “Customer Expectation,” “Feedback Loop,” “Service Standard,” “Agent Empowerment,” “Wait Time,” or “Handoff Clarity.” These expose systemic gaps in customer experience, not just process flaws.

What should I do if my team resists custom fishbone branches?

Start with a standard model and invite the team to critique it. Ask: “Which category doesn’t fit? Why?” This creates buy-in. Then co-create a new version. I’ve found that teams are more committed when they see their own logic reflected in the diagram.

Can I use fishbone categories with digital tools like Visual Paradigm?

Absolutely. Visual Paradigm support custom branching. Use color coding to distinguish between categories. If you’re working as a team, assign each branch to a facilitator to guide brainstorming. The structure works just as well digitally—often better, due to easier editing and version tracking.

What are the signs I need to re-evaluate my fishbone categories?

If you’re repeatedly finding causes in the same branch, or if the diagram feels unbalanced (e.g., 90% of causes under “People”), you may have missed a systemic domain. Reassess: Are we overlooking environmental, policy, or integration factors? Re-structure based on actual failure patterns.