The most interesting cases are complex systems where a fault/even results from a combination of multiple factors. In that case, asking for a "root" cause is unp

The most interesting cases are complex systems where a fault/even results from a combination of multiple factors. In that case, asking for a "root" cause is unproductive, and a better question to ask would be: how might the system be patched, with the least pernicious side effects. This is also why I don't always like the drive for more "accountability". As can be seen in the other HN thread on the front page about data driven medicine and the side effects on the healthcare system, you need to be very careful about which of the causes you decide to intervene on. When you closely manage something to reduce variation, you also lose any information you might get about the system from the variation of that quantity. This point is nicely made in another post on the same blog: http://reinertsenassociates.com/the-dark-side-of-robustness/ http://reinertsenassociates.com/the-dark-side-of-robustness/ Especially with reflexive systems (involving humans), the appropriate response might sometimes involve performing no intervention, or performing an intervention downstream, to modify its assumptions about what it receives (eg: adding error handling).