Something nice and topical. I just read these two items on the news:
Obama is in the lead by 50.4% to 48%, with 61% of votes counted. (Ohio)
With 86% of the vote counted, Virginia is still sitting on a knife edge. Romney is hanging on to a lead of 49.9%, but Obama is snapping at his heels on 48.7%.
Intuitively they sound like "dead certs" not "knife edge", because the populations involved must be huge. Then I realized I didn't know exactly what to do to prove my thesis.
Formalizing my thesis: I'm 99% sure that the current leader won't change once all votes are counted. But the question I have is: how many voters do there have to be in each state to be able to claim this?
NOTE: to be clear on definition, if there are N voters in Ohio, and Obama is leading 50.4:48 based on counting 0.61 x N votes, what is N to have 99% confidence that the Obama ratio will be >=50?
UPDATE: The comments have explained to me that the 86% was of precincts, not voters, with precincts supposed to represent around 2500 voters. But more importantly there may be an urban bias in the precincts that get counted last. If you wish to post an answer please assume my original assumptions: that it is 86% of actual voters, and that there is no bias in the votes counted so far. P.S. Apparently, Virginia ended up with Obama 1,868,191 (50.57%) to Romney 1,767,692 (47.85%).