Definition
A problem-solving tool for establishing the relationship between an outcome and its multiple causes.
In detail
Cause and Effect Diagram, also called fishbone diagram, is a tool for systematically sorting out potential causes of a problem. It places the problem outcome at the fish head and expands possible causes into fishbones by categories of Man, Machine, Material, Method, Environment, Measurement (6M); for transactional processes, 4P is used instead, helping teams brainstorm from multiple dimensions and identify all possible influencing factors. It solves the problem of guessing from experience and missing key causes when facing complex problems. Unlike simple brainstorming, the Cause and Effect Diagram provides a structured classification framework, making analysis more comprehensive. Its output is usually a visual cause diagram that provides direction for subsequent data collection and root cause analysis.
Example in practice
A factory has recently seen a rise in its defect rate, so the team holds an analysis meeting. They first draw a Cause and Effect Diagram, write the Problem "rising defect rate" in the fish head, and then list possible causes one by one across the six aspects (6M): Man (operator skill), Machine (equipment precision), Material (raw material batch), Method (work standards), Environment (workshop temperature and humidity), and Measurement (measuring instruments). Through this diagram, the team finds that they had previously focused only on operator factors while overlooking equipment aging, so they decide to prioritize equipment inspection and repair.