Cause and Effect Diagram
A structured breakdown tool that maps possible causes so you can trace an undesired result back to its underlying root cause.
Key Points
- Also called a fishbone or Ishikawa diagram; it visually links causes to an effect.
- Organizes potential causes into categories (e.g., Methods, Materials, People, Equipment, Environment, Measurement).
- Supports team brainstorming and root cause analysis during quality management and problem solving.
- Often used with the 5 Whys and Pareto analysis to validate and prioritize likely root causes.
Example
A web project experiences slow page loads in production. The team builds a fishbone with categories such as Code, Database, Server, Network, Configuration, and Traffic. By exploring each branch, they find an unindexed database column causing a heavy query. After adding the index and optimizing the query plan, performance returns to target.
PMP Example Question
During Control Quality, the team wants to systematically explore and categorize reasons for recurring defects to find the root cause. Which tool should the project manager use?
- Pareto chart
- Scatter diagram
- Cause and Effect Diagram
- Control chart
Correct Answer: C — Cause and Effect Diagram
Explanation: A cause and effect (fishbone) diagram organizes possible causes under logical categories to trace a problem back to its root cause.
