5 Whys
Simple issues
Ask "why" repeatedly until you reach the root cause
Best forSimple to moderate issues
Fishbone
Multi factor
Organises causes across People, Process, Equipment, and more
Best forMulti factor problems
Fault Tree
Technical
Maps the logical relationships between failures in a top down tree
Best forComplex technical failures
FMEA
Proactive
Scores failure modes by severity, likelihood, and detectability
Best forProactive risk assessment
Timeline
Sequenced
Reconstructs the order of events to reveal where things went wrong
Best forIncidents with a clear sequence