A team is investigating ways to reduce power outages. They determine that an outage can occur in only three ways: grid failure, local transformer…

A tree diagram (systematic diagram) starts with a single statement—here, “power outage”—and “fans-out” hierarchically into increasingly detailed branches: first the three outage modes (grid, transformer, overload) and then their underlying causes. It is the standard Seven Management & Planning tool used to break a broad problem into successively finer levels of detail for root-cause exploration, exactly matching the description given.

A. Affinity diagram – clusters like ideas without hierarchical branching; no “handle” or fan-out structure.
B. Inter-relationship digraph – displays causal links among factors, not a top-down decomposition.
D. Process decision program chart – extends a tree to foresee counter-measures to potential failures; not indicated here.
E. Matrix diagram – cross-tabulates relationships between two (or more) sets of items; no fan-out.
F. Prioritization matrix – ranks options using weighted criteria, not used for cause breakdown.
G. Activity network diagram – sequences tasks over time (PERT/CPM); unrelated to causal analysis.

1. The Certified Six Sigma Black Belt Handbook

3rd ed.

ASQ Quality Press

2014

Chapter 11 “Seven Management & Planning Tools

” pp. 354-356 – definition and example of Tree Diagram.

2. Pyzdek

T. & Keller

P. The Six Sigma Handbook

5th ed.

McGraw-Hill

2018

Section 9.3 “Tree (Systematic) Diagram

” pp. 292-294 – describes “fan-out” from a single problem statement to detailed causes.

3. Brassard

M. & Ritter

D. The Memory Jogger II

GOAL/QPC

2nd ed.

2010

pp. 193-196 – illustrates tree diagrams starting with a “handle” and branching to root causes.

4. University of Michigan

IOE 481/483 Course Notes

“Seven Management Tools

” Lecture 6

slides 9-11 – hierarchical problem decomposition via Tree Diagram (OCW repository).