Root Cause Analysis (Fishbone/Ishikawa Diagram)
Root cause analysis investigates why a problem occurs. A fishbone, or Ishikawa, diagram organizes possible causes into categories so they can be investigated; the diagram alone does not establish which causes are responsible.
THE IDEA
Root Cause Analysis (RCA) is a systematic approach to identify the underlying causes of problems or defects. In Lean methodology, RCA is applied not only to major issues but also to minor inefficiencies and near misses, as they can accumulate or signal larger risks.
The fishbone diagram, also known as the Ishikawa diagram, is a visual tool that organizes potential causes into categories. Common categories include:
- Manpower (people)
- Methods (processes)
- Machines (equipment)
- Materials (inputs)
- Measurement (data)
- Environment (work conditions)
However, the categories can be customized. A modified fishbone includes categories like: realistic goals, roles and responsibilities, human factors, resources, priorities, and dilemmas. The key is to focus on 'why' rather than 'who' or 'what'.
When to use it
Investigating the cause of a customer complaint spike in a call center.
Analyzing why a marketing campaign failed to meet its targets.
Identifying reasons for high employee turnover in a department.
Determining why a software project missed its deadline.
FROM THEORY TO EVERYDAY LIFE
In practice
Manufacturing Defect Reduction
In a hypothetical factory, a team uses a fishbone diagram to propose inadequate training, outdated machinery, and poor raw materials as causes of defects. Investigation supports those explanations; after corrective work, defects fall by 50%. The percentage is illustrative, not a reported case result.
Software Bug Prevention
A software team uses a fishbone diagram to group possible contributors to release bugs, including unclear requirements, gaps in testing, and version-control problems. The team investigates those possibilities before deciding which changes to make.
A MOMENT TO REFLECT
Put it to work.
Think of a recent problem. Which possible causes would you put on a fishbone diagram, and how would you investigate them?
Why is it important to consider minor issues and near misses in RCA?
How can the categories in a fishbone diagram be customized to your industry?
Often confused with
CONTINUE THE CONVERSATION
Source texts
- Beyond the Five Whys Root Cause Analysis and Systems Thinking (James C. Paterson)