Step 9 · Root-cause method
Root-cause analysis
Expert mode offers any of the RCA methods. Remember the separation the pack requires: the mechanism is what physically happened; the root cause is the correctable reason those conditions existed or were not controlled.
Cause-and-effect (Fishbone / Ishikawa)
5 Whys
Change / Difference Analysis
Events & Causal Factors (timeline)
Barrier Analysis
FMEA / FMECA
Fault Tree Analysis
FMEA / FMECA
Compare the actual failure with anticipated failure modes; check whether the mode existed in a prior FMEA, whether severity/occurrence/detection were underestimated, and whether controls were absent or weak. Prioritise actions on evidence, not RPN alone.