Cause-effect Diagram
A cause-effect diagram is a visual tool used to identify, organize, and analyze the possible causes of a specific problem or defect.
“A graphical representation used to organize and display the interrelationships of various possible root causes of a problem. Possible causes of a real or potential defect or failure are organized in categories and subcategories in a horizontal tree-structure, with the (potential) defect or failure as the root node.”
(Definition reproduced from the ISTQB Glossary. Copyright belongs to ISTQB.)
View the complete ISTQB GlossaryWhat is Cause-effect Diagram?
Also known as a fishbone or Ishikawa diagram, a cause-effect diagram helps teams systematically explore potential root causes before deciding on corrective actions.
Structured analysis: Causes are grouped into logical categories for easier investigation.
Root cause analysis: The diagram encourages teams to look beyond symptoms.
Collaborative technique: Multiple stakeholders contribute ideas during analysis sessions.
Real World Example
A regulated product team is preparing a release where Cause-effect diagram appears in reviews, test design conversations, or defect triage rather than as an isolated glossary word.
The risk is that the team treats Cause-effect diagram as interchangeable with nearby ISTQB terms. That makes test scope blurry and can lead to weak evidence for the release decision.
The tester anchors the discussion in the official definition, asks where the concept appears in the product, and designs examples that show the difference between Cause-effect diagram and similar ideas.
The page becomes useful in practice because Cause-effect diagram is connected to a specific testing decision, not memorized as a detached definition.
Practice Questions
Question 1
Which activity BEST suits a cause–effect diagram?
Question 2
What’s a COMMON mistake with fishbone diagrams?
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