Why No Science of Nerds?
slatestarcodex.com
slatestarcodex.com
Not if the traits are correlated with each other. The chosen binary math treatment works only if the traits are independent, i.e. mutually orthogonal. They aren't -- nerdy traits are strongly correlated, so much so that if you find any five of the nine traits in an individual, you're most likely already done identifying a nerd.
Also, there's a more efficient way to express a fractional probability: 1/a^b = a^-b.
It is true that there is a certain amount of informality in the wording of the quoted paragraph, however. I agree that the author shouldn't have glossed over it. He does clarify later though, which makes the whole thing not so much of a big deal, especially as it's the very next paragraph.