When things go wrong it is crucial that when trying to identify a fault, you conduct investigations systematically.

Systematic fault finding should include, brainstorming potential root causes from multiple aspects, as well as proper documentation of any findings.

A Fishbone Diagram (also known as an Ishikawa Diagram or Cause-and-Effect Diagram) is a visual tool used to systematically identify and analyze the root causes of a problem.

It looks like a fish skeleton, with the main problem (effect) at the "head" and potential causes branching off the "spine" like bones.

The Fishbone Diagram originated in Japan and was created by Kaoru Ishikawa in the 1960s. Ishikawa was a professor at the University of Tokyo and a pioneer in quality management practices.

He introduced the diagram as a tool for quality control, especially in industrial and manufacturing settings.

His goal was to help teams identify root causes of problems in a structured and visual way, making it easier to improve processes. That’s why it’s also called the Ishikawa Diagram — named after him.

Let’s break down how a Fishbone Diagram works and how it can be utilized.

Anatomy of the Fishbone Diagram

Head (Effect): At the right, write the problem or effect you want to analyze (e.g., “Low Product Quality”).

Spine: A horizontal line leading to the head; this is the diagram’s backbone.

Primary Bones (Major Categories): Branching off the spine are main cause categories. Common sets include:

• 6 Ms (Manufacturing): Machine, Method, Material, Manpower, Measurement, Mother Nature (Environment)

• 4 Ps (Service): Policies, Procedures, People, Place

• 8 Ps (Marketing): Product, Price, Place, Promotion, People, Process, Physical Evidence, Performance

Secondary and Tertiary Causes: For each major category, draw smaller bones to list more specific potential causes.

How It Works

Define the Problem

Begin by pinpointing the exact issue you aim to address.

Craft a short, precise statement that outlines what’s occurring, the location of the problem, and the time frame in which it emerged.

This clear description serves as the “head” of your Fishbone Diagram, aligning the team’s understanding before you proceed.

Select Categories

Next, choose the major cause categories relevant to your context—such as the 6 Ms for manufacturing or the 4 Ps for services.

These categories become the main “bones” branching off the spine, providing a framework to organize potential causes effectively.

Brainstorm Causes

Gather your team and brainstorm all possible factors that might contribute to the problem under each chosen category.

Capture every idea, no matter how unlikely, as branches off the corresponding “bones,” laying the groundwork for deeper analysis.

Let’s break down a manufacturing problem using the 6M’s strategy.

Manpower - This includes the human element—skills, training, experience, and attitudes of workers involved in the process. Human error, fatigue or insufficient training can contribute to defects or inefficiencies.

Machine - This refers to the equipment, tools and technology used in the manufacturing process. Issues may arise from machine wear and tear, poor maintenance, incorrect settings or outdated technology—all of which can affect product quality and efficiency.

Method - This involves the procedures, workflows and techniques used to perform tasks. Inconsistent or poorly defined methods can lead to variability in outcomes.

Material - The raw materials or components used in production. Variations in material quality, supplier differences or contamination can significantly impact the final product.

Measurement - Refers to the tools and systems used to measure performance, quality and process accuracy. Faulty instruments or inconsistent measurement methods can lead to incorrect conclusions and defective products.

Mother Nature (Environment) - The physical and environmental conditions where manufacturing takes place. Temperature, humidity, dust, lighting or noise can influence both machines and humans, impacting quality and safety.

Example Use Case

Problem: “Customer complaints about late deliveries.”

• Manpower

  • Understaffed warehouse leads to picking delays

  • Insufficient training results in order-packing errors

• Method

  • Inefficient order-processing workflow creates bottlenecks

  • Lack of standardized procedures causes inconsistent handling

• Machine

  • Aging packaging equipment operates below capacity

  • Unscheduled maintenance results in unexpected downtime

• Material

  • Stock shortages delay order fulfilment

  • Inaccurate inventory records cause rework and hold-ups

• Mother Nature (Environment)

  • Warehouse capacity constraints lead to congestion and slow throughput

  • Severe weather disrupts transportation schedules

• Measurement

  • Inaccurate delivery-time tracking masks true performance

  • Lack of real-time monitoring prevents proactive issue resolution

Dig Deeper

Once you’ve listed initial causes, probe further by asking follow-up questions for each. “Why does this happen?” and add the resulting sub-causes as smaller branches.

This deeper exploration helps you peel back layers and approach the root issues.

Manpower

• Understaffed warehouse leads to picking delays

  • Dig Deeper: Why understaffed? → High turnover due to low morale

• Insufficient training results in order-packing errors

  • Dig Deeper: Why insufficient? → No onboarding checklist or schedule

• Method

  • Inefficient order-processing workflow creates bottlenecks

    • Dig Deeper: Why inefficient? → Manual approvals slow down order release

  • Lack of standardized procedures causes inconsistent handling

    • Dig Deeper: Why no standards? → SOPs are outdated and not enforced

• Machine

  • Aging packaging equipment operates below capacity

    • Dig Deeper: Why aging? → Deferred capital investment

  • Unscheduled maintenance results in unexpected downtime

    • Dig Deeper: Why unscheduled? → No preventive maintenance plan in place

• Material

  • Stock shortages delay order fulfilment

    • Dig Deeper: Why shortages? → Safety stock levels set too low

  • Inaccurate inventory records cause rework and hold-ups

    • Dig Deeper: Why inaccurate? → Barcode scanners not integrated with WMS

• Mother Nature (Environment)

  • Warehouse capacity constraints lead to congestion and slow throughput

    • Dig Deeper: Why constrained? → Poor layout planning reduces usable space

  • Severe weather disrupts transportation schedules

    • Dig Deeper: Why severe impact? → No backup carrier arrangements

• Measurement

  • Inaccurate delivery-time tracking masks true performance

    • Dig Deeper: Why inaccurate? → GPS data not synced in real time

  • Lack of real-time monitoring prevents proactive issue resolution

    • Dig Deeper: Why lacking? → Dashboards aren’t configured for alerts

Analyze & Prioritize

With your diagram complete, review all identified causes and determine which are most likely driving the problem.

Prioritize these key factors, perhaps using techniques like the 5 Whys or Pareto analysis, to focus your improvement efforts where they’ll have the greatest impact.

After digging deeper into the causes, we can analyze the impact and prioritize actions.

For this example, key priorities could include addressing staff retention to reduce delays from under staffing, implementing preventive maintenance for equipment, and improving inventory management through better stock levels and WMS integration.

By breaking down potential contributing factors you can focus on the primary areas first, with this your organization can address the root causes and have the greatest impact on your problem.

Summary

Fishbone diagrams work so well because they turn a messy tangle of possible causes into a neat, easy-to-follow picture.

You start with the problem and then, as a team, map out all the factors that could be at play, then dig deeper into each one.

This collaborative, step-by-step approach not only surfaces hidden issues but also helps everyone agree on what really needs fixing.

It’s a simple way to get to the heart of persistent problems and figure out where to focus your efforts.

Benefits:

• Structured Visualization: Shows how various factors interplay to create a problem.

• Collaborative Exploration: Encourages team brainstorming and diverse perspectives.

• Root Cause Focus: Helps prevent fixing only symptoms by drilling down into deeper causes.

• Versatility: Applicable to manufacturing, service, healthcare, marketing, and more