Kaung Myat Tun

let’s dive into the Cause and Effect Diagram, also known as the Ishikawa Diagram or Fishbone Diagram. It’s a powerful tool for root cause analysis, quality management, and continuous improvement — and it does appear in the PMBOK® Guide as a model for problem-solving.

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🐟 What is a Fishbone Diagram (Cause and Effect Diagram)?

A Fishbone Diagram visually maps out the possible causes of a problem, helping teams identify, analyze, and solve the root causes rather than symptoms.

It’s called a “fishbone” because the diagram looks like a fish skeleton:

• The head is the problem (effect)
• The bones are categories of potential causes

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🧠 Use in PMP Context

• Tools & Techniques in:
  • Root Cause Analysis
  • Manage Quality (process 8.2)
  • Control Quality (process 8.3)
• Commonly used in problem-solving sessions, retrospectives, and corrective action planning

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📘 Typical Categories in a Fishbone Diagram (6M for manufacturing)

Category	Description
Man (People)	Human factors (skill, fatigue, training)
Machine	Tools, technology, software, hardware
Method	Procedures, workflows, practices
Material	Input quality, raw data, software versions
Measurement	Metrics, accuracy, KPIs
Mother Nature (Environment)	External influences, weather, culture, working conditions

In software projects, “Machine” could be infrastructure and “Material” could be data or code.

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🧩 How to Build One (Steps)

1. Define the Problem (Effect):
   → Write this at the “head” of the fish.
2. Draw the Spine and Bones:
   → Create main categories as “bones”
3. Brainstorm Causes:
   → Under each category, list possible causes
4. Drill Down:
   → Keep asking “why?” to find root causes
5. Analyze and Prioritize:
   → Highlight the most likely or impactful causes

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🎯 PMP Example Scenario

Problem: High defect rate in delivered software
Fishbone categories might reveal:

• Inadequate testing (Method)
• Under-trained staff (Man)
• Unstable test environment (Machine)
• Poor user stories (Material)
• Lack of defined quality metrics (Measurement)

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📊 Sample Diagram Layout

lessCopyEdit                  |→ Cause A1
      Category A →|→ Cause A2
                  |
Problem --------> |
                  |→ Cause B1
      Category B →|→ Cause B2
                  |

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🧠 PMP-Style Practice Question

Your project has experienced repeated delays in deployment. You want to identify the root causes involving people, processes, and tools. Which tool should you use?

A) Scatter diagram
B) Pareto chart
C) Fishbone diagram
D) Control chart

✅ Correct Answer: C
Explanation: The Fishbone Diagram is used to categorize and analyze root causes.

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✅ Summary

Term	Also Known As
Fishbone Diagram	Cause-and-Effect Diagram, Ishikawa Diagram
Used For	Root Cause Analysis
Related PMBOK Areas	Manage Quality, Control Quality
PMP Exam Type	Tool selection, scenario-based analysis