root cause

Published data gives an interruption rate, and replacements are a fraction of interruptions, so the comparison needs care before it means anything. The derivation that turns one into the other, the answer for a healthy fleet, and the four cuts through the data that turn an anomalous number into a cause.

Everyone has this story and most candidates tell a flattering version of it. The bias that produces almost all of these mistakes, the cost you have to be willing to name, and the process change that is the difference between an anecdote and a lesson.