I have a question to me fellow readers.
On of the most famous Lean tools (or quality tool as well) is the Five Whys. Literature has it that one should ask 5 whys at least and that a further number of whys isn’t a bad thing. Yet, Taiichi Ohno often gives examples where the investigation is stopped at the fifth why despite one could easily have asked some further ones.
Aside from the usual caveats (doing wide whys and forgetting to go deep five levels; assigning blame to other people; etc.), what are your practices regarding five whys, and what’s your criteria for stopping?
Here’s my answer below, but please only read it after you have posted your own in a comment this post (double-click the following paragraph to have it decoded in a pop-up – an alternative way is copy-pasting the text onto www.rot13.com website).
[rot13]My own criteria for stopping analysis is when people end up with a cause that has not other further cause beside “well, we just have to do X”.[/rot13]