What does “Fishbone diagram” mean?
Short answer
A fishbone diagram maps the possible causes of one problem on branches, like fish bones. Teams also call it a cause-and-effect or Ishikawa diagram.
Also known as: Ishikawa diagram, cause and effect diagram, cause-and-effect diagram
What it is
IHI defines a cause and effect diagram as a graphic tool to explore and show the possible causes of an effect.
Use the classic fishbone when causes fit groups like materials, methods, equipment, environment and people. Or use a process-type diagram to show causes at each step.
IHI lists three benefits. It shows a team that many causes add up to an effect. It shows how causes relate to the effect and to each other. And it helps find areas to improve.
How to use it
- Write the problem at the head, specific and measurable.
- Draw branches for the groups that fit.
- Brainstorm causes with the people who do the work.
- Mark the likeliest causes. Check each against data before you accept it.
Example: late first-case starts at a surgery center. Branches might hold people (arrival times), methods (room turnover steps), equipment (instrument trays not ready) and materials (supply stock-outs).
Mix-up: a fishbone lists possible causes and does not prove them. Combine it with five whys and check records.
The VA's version works backward with 'caused by' and asks for at least two causes: an action and a condition. In IncidentKit, investigations record contributing factors.
Frequently asked questions
Why is it called a fishbone diagram?
The problem sits at the head of a long spine, and cause groups branch off like ribs, like a fish skeleton. It is also called an Ishikawa or cause and effect diagram.
Which categories should a fishbone use?
IHI's classic version uses materials, methods, equipment, environment and people. Switch to a process-type diagram or change the groups when causes do not fit.
Does a fishbone find the root cause?
No. It lays out possible causes. Check each one against records, observation and interviews. Confirmed causes lead to corrective actions.
Sources
- IHI: Cause and effect diagram (QI Essentials toolkit)
- VHA National Center for Patient Safety: Root cause analysis (page and Guide to Performing a Root Cause Analysis, rev. 02/05/2021)
Reviewed against the sources above on Oct 5, 2026. Rules change: confirm current requirements with the issuing body or your counsel before relying on any summary.
Put the definition to work.
IncidentKit turns these terms into workflow: reports, investigations, corrective actions and packets.