The “5” is a reminder to avoid shallow attribution
When faced with a problem, there’s a general tendency for people to only consider the immediate contributing factors.
The “5” in “5 Whys” is a reminder to go beyond shallow attribution and keep exploring underlying causes.
“5” is a heuristic not a fixed number
In practice, the number of whys can be less or more than 5. Because of the tendency to be shallow, I’d still suggest thinking about it more if it ends up being less than 5.
5 Whys, not 5 Whos
The use of “why” is to remind us not to default to blaming people, especially their motivation (aka fundamental attribution error), and consider broader factors for why something happened.
See also Six Sources of Influence.
“How” seems clearer than “Why”
The purpose of root cause analysis is to understand mechanism(s) to allow us to come up with better ideas for how to intervene. “How” expresses this more clearly than “Why”.
But there’s usually more than one root cause!
There is no assumption that there is a single root cause. It’s not called “single root cause analysis”.
The idea is that you’re exploring a single promising factor with 5 Whys. This does not mean you won’t…