As Steve LeVine notes, Nassim Taleb would take one look at that reasoning and simply laugh. For one thing, how on earth is it possible to determine that the risk of an overcharge is less than or equal to one in a billion? Probabilities that small simply can’t be measured. And more importantly, how did Boeing determine that the probability of a fire absent an overcharge was zero? There’s good evidence that neither of the battery fires were caused by an overcharge — but Boeing seems to have decided that fires caused for any non-overcharge reason were, literally, impossible. Once again, it’s incredibly hard to conceive of any coherent line of reasoning which could come to that conclusion.
But somehow the FAA accepted Boeing’s analysis at face value, and allowed Boeing to install lithium batteries on its planes, just as long as certain safeguards were put in place.
This is the same kind of literal quantitative thinking which helped cause the financial crisis. Put engineers in charge of something, and they’ll measure what they can measure, they won’t measure what they can’t measure, and they’ll protect against only the things they managed to foresee. And as all of us who spend our lives surrounded by electronic devices know, sometimes they fail. In a sense it doesn’t matter what the reason is: failure is just a fact of life, which is a real problem when failure could mean the fiery death of hundreds of people.
via Annals of quantitative overconfidence, Boeing edition | Felix Salmon.