5Why emphasizes asking 'why' in layers based on facts and data. The template provides branches for recording and verification, avoiding oral conclusions that cannot be traced.
It can be used in conjunction with Fishbone Diagrams and 8D D4.
Each layer of response should be supported by evidence or observable phenomena; when multiple branches appear, they should be verified separately rather than forced into a single narrative.
Stop at the system/process level where action can be taken, no need to fill all five layers.
Avoid substituting verification with guesswork; when there is a large difference in team levels, there is a bias towards attributing causes to lower levels.
For cross-departmental issues, designate a facilitator to prevent the discussion from diverging.