Friday, October 17, 2008

The Probability of an Obama Victory

An excellent statistical guide to the election's ongoing state-of-play is the website '' - According to its latest calculation, the probability of an Obama victory is 94.7%, compared to just 5.3% for McCain.

There's an important qualification to make here, though: the percentages above are equivalent to predicting what would happen were there 1,000 elections held simultaneously on Election Day - Obama would win around 947 of them, and McCain just 53. But here's the thing: there aren't going to be a thousand elections on November 4th, just one. McCain's hope will be that one of those 53 possible combinations comes up for him on the day.

For Obama supporters then, the key will be voter turnout - ensuring that the swing states that are leaning his way at present go for him on election day, when the polls really count.


Anonymous said...

Mr actuary here again. Let's look at the probabilites analysis. Is that based upon known distributions of votes or predicted distributions based on sampling? I know you know the answer. So just to be accurate what that analysis is saying is there is roughly a 5% chance McCain will win based on the polls. If the distribution were actually known and matched the polls the odds would be radically less. Do you agree?

Anonymous said...

voter turnout is key! i hope young people come out in droves to vote. they are the ones that will help obama glide into the oval office. the polls are a little scary, because i hope people dont think they dont need to vote because its looking really good for obama. and young people are notorious for saying they will vote but dont at the last minute. its all very frustrating and i cant wait till its over!

Kristie said...

Thank you, Daniel, for that very interesting mathematical perspective. As an American Democrat, I sincerely hope the odds are in Obama's favor. I also want him to win because if he does, I feel that, based on American history, we will then be prepared to accept a woman president in the near future. As far as female leaders, the UK is so far ahead of us.

Anonymous said...

Hey Daniel, I think your statistical analysis is very enlightening.

I made a prediction map today to use for a betting pool. My bets included all of the states listed in the website you provided,, with the exception of Ohio and Florida.

I realize that it is statistically favorable (according to the polls) for both Ohio and Florida to vote democrat. I based my decision on the last two elections, in which Ohio and Florida both went republican even after polling democrat.