I think the conclusion is super interesting: "HROs commonly aim for a reliability rate of ‘six sigma’ (three errors per million opportunities). By these measur

I think the conclusion is super interesting: "HROs commonly aim for a reliability rate of ‘six sigma’ (three errors per million opportunities). By these measures, healthcare is struggling to move beyond two sigma (308 500 errors per million opportunities, or a 30.85% error rate). [...] But healthcare is far more complex than automobile manufacturing, and takes place amid processes and systems that are woefully underdesigned in comparison to a modern factory. [...] As a result, approaches developed for solving problems in the automotive manufacturing context may not be as effective in the healthcare arena." So, in a way, the problem isn't really with 5 Whys. The problem is that it's applied to processes where errors/defects are much more common. I've seen it applied to my own domain as well, keeping computer systems (web sites, mainly) running. If we have one incident with possible downtime per year, there are probably still way too many potential root causes for 5 Whys to be useful... and that's still probably at least a magnitude better than anything I've personally worked on.