An Issue Tree (also called a logic tree or hypothesis tree) is a structured problem-decomposition tool that breaks a complex question into progressively smaller, answerable sub-questions. Used by McKinsey, BCG, and Bain to structure consulting engagements, issue trees ensure no aspect of a problem is overlooked and that analysis is focused on questions that actually matter for the conclusion.
MECE (Mutually Exclusive, Collectively Exhaustive) is a problem-structuring principle developed at McKinsey & Company that ensures all components of a problem are covered without overlap. Mutually Exclusive means no duplication between categories; Collectively Exhaustive means nothing is left out. MECE structures produce clear, complete, non-redundant analyses — the foundation of consulting problem-solving and a critical discipline for any complex analysis.