A hierarchical map that shows a project or process broken down into increasing levels of detail. It starts with the main objective or top-level view and successively branches out into smaller and smaller components, showing the relationships involved in greater detail.
In statistics, a tree diagram is used to list out all possible outcomes of an event and their associated probabilities. In Six Sigma the tree diagram is used for many different purposes. It can be used to translate "Voice of the Customer" (VOC) data from general ‘wants’ and ‘needs’ into specific Critical to Quality Characteristics, or CTQCs. The Cause & Effect diagram (also called Fishbone or Ishikawa diagram) is also a type of tree diagram that helps identify the potential root cause(s) of a problem.
The possible sources of information for a tree diagram are:
• Brainstorming by the team based on prior experiences.
• Data collected from Check Sheets or other sources.
The tree diagram is very useful and versatile tool with many advantages:
• Straightforward and easy to learn.
• Organizes discussion to stay focused on the issues at hand.
• Promotes visual linkages between an objective and its components.
• Helps prioritize further analysis and corrective actions.
ASQ's Toolbox - Tree Diagram - http://www.asq.org/learn-about-quality/new-management-planning-tools/overview/tree-diagram.html