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Saturday election prediction


October 20 2012

In tonight's prediction, I am using Nate Silver's numbers from yesterday which can be seen at to see how likely each candidate is to win, and by how many electoral votes.

To make these numbers, I ran 100,000 simulated presidential votes; this is a type of simulation called a "Monte Carlo" simulation.

No correlation between states

Assuming there is no correlation between the states, we get the following numbers. In other words, I am assuming that Obama getting Ohio does not affect his chances of getting Florida, and vice-versa.
Romney 13.6%
Tie      .8%
Obama  85.6%
These numbers more favor Obama than Wednesday's numbers; it appears he is getting a post-second-debate bounce.

By state

In these numbers, I have determined a given candidate's chances of winning based on them winning or losing a given state.
Obama gets OH
Romney   6.02%
Tie      0.56%
Obama    93.42%
Romney gets OH
Romney   32.85%
Tie      1.55%
Obama    65.60%

Obama gets FL
Romney   0.70%
Tie      0.10%
Obama    99.20%
Romney gets FL
Romney   20.99%
Tie      1.26%
Obama    77.74%

Obama gets CO
Romney   9.72%
Tie      0.76%
Obama    89.51%
Romney gets CO
Romney   18.68%
Tie      0.93%
Obama    80.39%

Obama gets NH
Romney   12.06%
Tie      0.93%
Obama    87.01%
Romney gets NH
Romney   17.27%
Tie      0.60%
Obama    82.13%
In the above blog, we look at the election probabilities based on various conditions. For example, if Obama wins Ohio, Romney has only a 6.02% chance of winning the election.

By electoral vote

Here are the chances of the incumbent (Obama) getting a certain number of electoral votes (EVs):
Obama EV
220-229    .1%
230-239    .4%
240-249   1.4%
250-259   4.1%
260-269   8.4%
270-279  14.2%
280-289  18.3%
290-299  18.3%
300-309  13.6%
310-319  11.2%
320-329   6.1%
330-339   3.0%
340-349    .7%

Mean   291.6
Median 290
"Mean" is adding up all of the possible EVs together and dividing by 100,000. Median is sorting by the number of electoral votes and choosing the middle one.

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