4Ms
The 4Ms are a way of classifying the possible causes of a problem in a production process into four categories: manpower, machines, methods and materials
What it means, how it is used and where it comes up, with its related concepts.
What it is and how it works
The name comes from the English initials Man (people or manpower), Machine, Method and Materials. It is mainly used as a guide for building a cause-and-effect or Ishikawa diagram, in which each category is a branch where the team notes candidate causes before investigating them.
Extended versions have since been proposed, such as the 5Ms or 6Ms, which add Measurement and environment (Milieu or Mother Nature), and service settings use other adapted categories. The classification does not explain a problem on its own: it helps make sure no type of cause is overlooked and is combined with techniques such as the five whys.
Also known as
Four Ms