Fishbone Diagram in Root Cause Analysis: A Comprehensive Guide

Quick Overview

1. A fishbone diagram visually organises potential causes of a problem into clear categories.

2. It supports root cause analysis by helping teams explore contributing factors systematically.

3. Common manufacturing categories include Methods, Machines, People, Materials, Measurement, and Environment.

4. Potential causes should be prioritised and validated with evidence before corrective action.

5. Fishbone diagrams support structured brainstorming but do not confirm root causes on their own.

Fishbone diagrams offer a clear way to explore the possible causes behind a problem by organising them into structured categories. Commonly used in root cause analysis, they help teams examine contributing factors, identify patterns, and investigate issues more systematically. 

This blog explains how fishbone diagrams work, how to create them, how to choose suitable cause categories, and where they are most useful.

What is a Fishbone Diagram?

A fishbone diagram, also known as an Ishikawa or cause-and-effect diagram, is a visual tool used in root cause analysis to organise potential causes of a problem into categories. Its name comes from its resemblance to a fish skeleton.

Did You Know?

Kaoru Ishikawa developed the cause-and-effect diagram and introduced the technique at Kawasaki Steel in the early 1950s. Its fish-like structure later inspired the name “fishbone diagram”, and the tool became widely used in quality management.

The problem or effect is placed at the diagram’s ‘head’, while major cause categories branch from the central spine and specific causes or sub-causes branch from them. The fishbone diagram is also recognised as one of the seven basic quality tools.

Steps to Create a Fishbone Diagram

Creating a fishbone diagram for root cause analysis involves a structured process for identifying, organising, and examining potential causes of a problem. Here are the key steps involved:

1) Identify the Problem

Clearly define the issue you're analysing. Write it at the "head" of the fish, usually on the right side of the diagram. Be specific to support an effective analysis.

2) Draw the Backbone

Start with a straight line from the left (the "tail") leading to the problem statement on the right. This line represents the fish’s backbone.

3) Choose Cause Categories

Identify broad categories that could contain factors contributing to the problem. Common manufacturing categories include Methods, Machines, People, Materials, Measurement, and Environment, while other industries can adapt the categories to suit the problem. These categories form the fish’s main ‘ribs.’

4) Add Category Branches

Draw slanted lines branching out from the backbone to represent each cause category. These resemble fish bones and provide space for listing the possible causes under each category.

5) Brainstorm Sub-causes

Under each category, list possible causes that may contribute to the problem and add smaller branches for relevant sub-causes. Involve team members with knowledge of the issue and ask ‘Why?’ where useful to explore causes at a deeper level.

6) Analyse and Prioritise

After listing the potential causes, review and evaluate each one to determine which are most likely contributing to the problem. Consider patterns, available evidence, and relevant expertise, then prioritise the strongest candidates for further investigation.

7) Validate Likely Causes

Use relevant data, observations, records, or tests to check whether the prioritised causes actually contribute to the problem. Validation helps distinguish plausible ideas from causes supported by evidence before corrective actions are selected.

Trainer’s Pro Tip

Document the evidence used to confirm or reject each likely cause. This creates a clear record of the analysis and makes it easier to revisit the findings if the problem occurs again.

8) Take Action

Once likely causes have been validated, develop appropriate corrective actions to address them and reduce the likelihood of recurrence. Assign responsibilities, define the required actions, and set suitable deadlines for implementation.

9) Review and Update

The fishbone diagram is not static. As you implement solutions and gather more insights, update the diagram to reflect new findings. Also, monitor the results of corrective actions to check whether they have reduced or resolved the original problem.

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How to Choose Categories for a Fishbone Diagram?

Choosing suitable categories helps organise potential causes and ensures the diagram reflects the problem being analysed. The categories should be relevant to the issue rather than following a fixed structure for every investigation. Here are some ways to select and refine the categories:

1) Understand the Problem Context

Before choosing the categories, make sure you fully understand the problem. Different issues require different categories, so think about what factors might be involved in your specific situation.

2) Customise Categories for Your Needs

Adjust the categories based on your industry or type of problem. For example, in customer service, "procedures" and "policies" might be useful, while in software development, "software" and "hardware" could be more relevant.

3) Engage the Team

Involve people from different roles who are familiar with the problem. Brainstorming as a team helps uncover overlooked aspects and ensures all relevant areas are covered.

4) Review Historical Data

Review historical data on similar problems. Past incidents can offer insights into which categories were important before and help you avoid missing key factors.

5) Be Open to Revision

Be ready to adjust your categories if needed. As you dive deeper into the analysis, you might realise some categories are too broad, too specific, or not relevant at all.

6) Ensure Comprehensive Coverage

Make sure the selected categories cover the main areas relevant to the problem. Broad coverage can help reduce the risk of overlooking important contributing factors.

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Example of a Fishbone Diagram

Fishbone diagrams are used across different domains to organise factors that could contribute to process failures, defects, or service problems. The following examples show how potential causes can be grouped for further investigation.

1) Fishbone Diagram for Customer Service Issues in a Call Centre

Problem Statement: High levels of customer complaints related to long wait times and unresolved queries.

For this example, suppose the preliminary investigation identifies the following observations:

A) Peak Complaint Times: Evenings and weekends

B) Call Types: Billing disputes and technical support requests

C) Employee Turnover Rate: High, with many new hires handling complex queries

D) System Downtime: Frequent slowdowns in the CRM system

E) Customer Feedback: Poor communication, unresolved issues, and long hold times

Fishbone Diagram Analysis – Potential Causes:

A) People:

a) High employee turnover, potentially contributing to a greater proportion of inexperienced agents.

b) Lack of proper training on handling technical issues.

c) Agents overwhelmed due to understaffing during peak hours.

B) Process:

a) Inefficient call routing system.

b) No clear escalation procedure for complex issues.

c) Lack of follow-up mechanisms for unresolved complaints.

C) Technology:

a) CRM system experiencing frequent downtime.

b) Slow response times due to outdated software.

c) Insufficient integration between different support tools.

D) Policy:

a) Unclear refund and dispute resolution policies.

b) Lengthy approval process for issue resolution.

c) Lack of consistency in handling similar customer concerns.

E) Communication:

a) Poor script design leading to repetitive questions.

b) Lack of personalised support.

c) Limited self-service options for simple queries.

Depending on which causes are confirmed, appropriate corrective actions could include:

a) Improve agent training and retention programmes.

b) Optimise call routing for faster resolution.

c) Upgrade the CRM system to reduce technical delays.

d) Revise customer service policies to support faster dispute resolution.

2) Fishbone Diagram for Healthcare Service Delays

Problem Statement: Long patient wait times within a healthcare facility.

For this example, suppose the preliminary investigation identifies the following observations:

A) Peak Times: Mornings and afternoons

B) Main Issues: Long wait times, poor communication, and delayed treatment

C) Staffing: Insufficient number of healthcare staff available during peak hours

D) Facility Design: Overcrowding in patient waiting areas

E) Patient Feedback: Complaints about slow response times and lack of coordination

Fishbone Diagram Analysis – Potential Causes:

A) People:

a) Staff shortages, leading to longer wait times.

b) Inadequate training, affecting quality of care.

c) High turnover rate, leading to inexperienced staff.

B) Process:

a) Long wait times due to inefficient patient scheduling.

b) Poor communication between departments, leading to delays.

c) Lack of a streamlined patient flow system.

C) Technology:

a) Outdated medical software, causing delays in data processing.

b) Lack of integration between patient management systems.

c) Slow response times from healthcare tech tools.

D) Environment:

a) Overcrowding in waiting areas, potentially reflecting or contributing to patient flow problems.

b) Poor facility design, hindering efficient patient movement.

E) Policies:

a) Inconsistent patient care protocols across departments.

b) Lengthy approval processes for necessary treatments or tests.

c) Administrative or treatment approval requirements, where applicable.

Depending on which causes are confirmed, appropriate corrective actions could include:

a) Increase staffing during peak hours to reduce wait times.

b) Implement cross-departmental communication tools for better coordination.

c) Upgrade medical software and improve system integration.

d) Redesign waiting areas and improve patient flow.

e) Streamline patient care protocols and approval processes.

Advantages and Disadvantages of Fishbone Diagrams in Root Cause Analysis

A fishbone diagram offers several advantages and limitations when exploring potential causes during root cause analysis. The following comparison highlights its key strengths and limitations:

Fishbone diagrams provide a structured way to explore the possible causes behind a problem and organise them into clear categories. When combined with evidence and validation, they can support more effective root cause analysis, helping teams move from possible causes towards well-informed corrective actions. Also, reviewing the results of these actions helps organisations assess whether the underlying problems have been addressed.

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