What is a Fishbone Diagram (aka Cause & Effect Diagram)?
A Fishbone Diagram is a structured brainstorming tool designed to assist improvement teams in coming up with potential root causes for an undesirable effect. Its name derives from its resemblance to the bones of a fish. It is also known as a Cause and Effect Diagram or an Ishikawa Diagram after its creator.
Causes are often grouped into major categories, which are classically defined as the 6 Ms (or the 6 Ps): Man/Mind Power (People), Method (Process), Machines (Program), Materials (Product), Measurements (Policy), and Milieu/Mother Nature (Place).
This tool is used in tandem with The 5 Whys.