A Tree diagram helps you break down big concepts into progressively greater detail. The idea here is to systematically breaking down a concept into its constituent pieces.

You would progress from left to right with the highest order items / most important concepts on the left. You would start with the “whys” and progress to the “hows. Alternately, you would start with the “goals” and progress to the “means” of achieving those goals.

This is a helpful tool to outline details relating to a problem, idea, process or a plan.

“If you choose not to decide, you still have made a choice.”

Rush lyrics

Tree diagrams benefit from affinity diagrams.

Tree Diagram Videos

Six Sigma Black Belt Certification Tree Diagram Questions:

Question: After the major headings of a tree diagram have been broken into greater detail, what is the next step that should be taken? (Taken from ASQ sample Black Belt exam.)

(A) Assemble the right team
(B) Review the diagram for logical flow and completeness
(C) Revise the problem statement
(D) Choose the tree diagram goal statement

Answer: (B) Review the diagram for logical flow and completeness.  A isn’t a great answer as you don’t always need a team for this activity. Even if you did, it would have been done long before the major headings were created. Similarly with D – you would have chosen the goal statement at the onset. C is tricky. I see that activity  – updating the problem statement on your charter – as something you might do at any time during a six sigma project depending upon what you find.


Question: A tree diagram can be used to do which of the following?

(A) Allow a team to identify root causes even when no credible data exist
(B) Show a causality relationship
(C) Present data from a check sheet
(D) Reveal the true level of a problem’s complexity

Answer: D) Reveal the true level of a problem’s complexity. We can eliminate A easily as there is no way to identify root causes without credible data or process information. Similarly, a tree diagram is used to graphically display increasingly complex layers of a problem, not to show causality. Data from a check sheet could be shown in a dot plot or other means, but not on a tree diagram.



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