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11/07/2012

Nate Silver on How He Got it Right: VIDEO

N_silver

The NYT numbercruncher discusses Obama's reelection win with Megan Liberman.

Watch, AFTER THE JUMP...

Posted Nov 7, 2012 at 8:30 AM EST by in 2012 Election, Nate Silver, News | Permalink

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Comments

  1. Well, it looks like Nate-boy gets laid this year!

    Posted by: Alex Parrish | Nov 7, 2012 8:33:26 AM


  2. Gay nerd power!

    Posted by: endo | Nov 7, 2012 8:50:56 AM


  3. And all the creaky old network idiots are sitting around saying: What the F just happened?

    Posted by: Byron St. James | Nov 7, 2012 9:06:05 AM


  4. Is Nate one of us? I hope so.

    Posted by: chasmader | Nov 7, 2012 9:11:51 AM


  5. Gay geek poster boy. Love him.

    Posted by: Frank O'File | Nov 7, 2012 9:27:58 AM


  6. ii love my geeks!

    Posted by: io | Nov 7, 2012 9:28:01 AM


  7. Funny how math and science work.

    Posted by: J. Alan | Nov 7, 2012 9:36:46 AM


  8. Nate is great. I can't have enough of FiveThirtyEight

    Posted by: Rafael | Nov 7, 2012 10:10:30 AM


  9. @chasmader - Yep, Nate is openly gay. :)

    Posted by: Nathan | Nov 7, 2012 10:44:56 AM


  10. If you compare the actual electoral map with his forecast, they seem to match in every state. Why is the number different? Obama got 303 electoral votes but his prediction was 313.

    Posted by: simon | Nov 7, 2012 10:50:24 AM


  11. @J Alan: So that's why Romney didn't write a concession speech - his pollster's use of dowsing rods didn't work;-)

    Posted by: Diogenes Arktos | Nov 7, 2012 10:54:53 AM


  12. It's uncanny that as advanced an art/science as statistics is, Nate appears to be the one who has mastered election forecasting. I am very impressed by him.

    I am sure there are statistics professors all over the country saying, well if I had wanted to I could have done that analysis. Maybe the Republicans should hire a few.

    Posted by: Fahd | Nov 7, 2012 11:08:21 AM


  13. I'm adding Nate Silver to my "Future Ex-Husbands List".

    Posted by: Profe Sancho Panza | Nov 7, 2012 12:39:03 PM


  14. I want John Turturro to play him in the movie.

    Posted by: DeeVee | Nov 7, 2012 12:49:12 PM


  15. Read his book. Fascinating read! Congrats, Nate.

    Posted by: jamal49 | Nov 7, 2012 2:27:08 PM


  16. @Simon. The reason for the difference is that the 313 EVs in Nate's model is an average of multiple runs of different scenarios. So, it basically means that Obama was fairly certain to get the 303 he got without Florida, and Florida was probably leaning toward Romney, meaning that its 29 EVs would show up for Obama in some model runs and for Romney in more runs.

    It's the same thing with the percentage prediction of an Obama victory (like 90%?). Obviously if he won all the states he was forecast to win based on polling averages (and he ultimately did), he has a 100% chance of winning. But given polling uncertainties and margins of error, when Nate runs his model multiple times it sometimes shows a Romney win.

    Fortunately for all of us, the real vote last night turned into a strong Obama win. So the models can take a rest and look ahead to 2014 and the Dems' hopes to hold onto the Senate.

    Posted by: Luke | Nov 7, 2012 3:36:02 PM


  17. As a reply to Simon's comment, "If you compare the actual electoral map with his forecast, they seem to match in every state. Why is the number different? Obama got 303 electoral votes but his prediction was 313."

    The 303 number does not include Florida, and the results for Florida are current not certain, If Obama wins Florida, he'll gain another 29 electoral votes. Since it's so close, it would add an average value of around 15 votes to a model that gave equal weight to each possible outcome. That puts the best guess between 303 and
    332 given the results that are currently in.

    BTW, Obama is slightly ahead in Florida in the vote count as of a short time ago, but it will take a while to be certain.

    Posted by: Bill | Nov 7, 2012 4:45:13 PM


  18. Regarding Fahd's comment: almost anyone familiar with statistics and the theory of probability can easily do the sort of analysis that Nate Silver did, although tracking down all the polls (state by state) could be a bit tedious. The one advantage that Nate Silver has is that, with lots of people paying attention to him and reading his blog, he can call Gallop or Pew and actually get to talk to someone who can provide details that would normally not be publicized - it is in the polling company's interest to cooperate with him so they get listed in his blog.

    He's also done a good job in packaging the results in a form that the general public can digest. But, the analysis is more or less straightforward - and I might add that he seemed to say that in one of the TV interviews. It's just that most journalists/pundits, at least in the U.S., have a very poor grasp of mathematics.

    Posted by: Bill | Nov 7, 2012 9:49:12 PM


  19. Thank Luke and Bill for the explanation. I still think it would be more realistic to put into the model the assumption that the electoral votes can't be split between both candidates. In other words, if the poll average of a candidate in the state is over 50%, he will get all the votes. That would be easy. You just look at the predicted electoral map and add up the votes for the blue states.

    Posted by: simon | Nov 7, 2012 11:29:15 PM


  20. As a follow up to Simon's comment (11:29:15 PM), the assumption is that electoral votes (for Florida) cannot be split between two candidates. So, Obama had about a 50/50 chance of getting either 0 or 29 electoral votes for Florida. If the probability of 0 votes is p and 29 votes is q, then the mean is 0p + 29q. The error is the square root of [(0-x)(0-x)p + (29-x)(29-x)q] and it turns out that this is a minimum when x is the mean value, 14.5 when p and q are both 1/2. You do better by being slightly off in both cases than by being way off half the time.

    Summing electoral votes for all the states works similarly - after summing, the result is close to a normal distribution (the bell-shaped curve you'll see in statistics books) centered on the sum of the mean values for each state.

    Posted by: Bill | Nov 8, 2012 2:11:16 AM


  21. For those who are curious, if each state gives all its electoral votes to the winner in that state and the polls show no advantage for either candidate in either state, the following shows the number of elections out of a total of 1 million in which a candidate gets a particular number of electoral votes (just including the range 200 to 340). You'll see the peak at about 270. It took under 30 minutes to put it together, including collecting the number of electoral votes per state, writing a program, and running it.

    200 3337
    201 3353
    202 3442
    203 3607
    204 3599
    205 3776
    206 3848
    207 3850
    208 3976
    209 4093
    210 4187
    211 4351
    212 4359
    213 4545
    214 4502
    215 4592
    216 4745
    217 4770
    218 4868
    219 4936
    220 4977
    221 5252
    222 5217
    223 5275
    224 5445
    225 5471
    226 5640
    227 5643
    228 5719
    229 5674
    230 5807
    231 5920
    232 6146
    233 6160
    234 6131
    235 6259
    236 6222
    237 6405
    238 6361
    239 6603
    240 6567
    241 6631
    242 6915
    243 6713
    244 6791
    245 6903
    246 6792
    247 6847
    248 7109
    249 7087
    250 7071
    251 7238
    252 7188
    253 7303
    254 7394
    255 7380
    256 7328
    257 7426
    258 7424
    259 7265
    260 7309
    261 7356
    262 7464
    263 7552
    264 7495
    265 7660
    266 7508
    267 7634
    268 7603
    269 7654
    270 7507
    271 7655
    272 7526
    273 7421
    274 7539
    275 7511
    276 7422
    277 7511
    278 7427
    279 7290
    280 7314
    281 7265
    282 7309
    283 7203
    284 7277
    285 7267
    286 7307
    287 7156
    288 7145
    289 6925
    290 6934
    291 7174
    292 6883
    293 6795
    294 6798
    295 6806
    296 6616
    297 6833
    298 6600
    299 6469
    300 6397
    301 6352
    302 6307
    303 6244
    304 6166
    305 5961
    306 6134
    307 5860
    308 5946
    309 5811
    310 5716
    311 5682
    312 5535
    313 5387
    314 5399
    315 5414
    316 5140
    317 5203
    318 4988
    319 4876
    320 4926
    321 4724
    322 4692
    323 4625
    324 4486
    325 4382
    326 4314
    327 4209
    328 4079
    329 4056
    330 3963
    331 3816
    332 3788
    333 3746
    334 3718
    335 3471
    336 3481
    337 3453
    338 3384
    339 3258
    340 3225

    Posted by: Bill | Nov 8, 2012 2:56:18 AM


  22. @Simon: There are states where the electoral votes do not all go to the winner. I remember seeing that on the live TR blog election night.

    Posted by: Diogenes Arktos | Nov 8, 2012 3:16:29 AM


  23. it makes my heart sing that there are people so dedicated like Nate who CARE about truth and accuracy. The icing on the cake is that he shares my gayness! Gay geeks will inherit the earth and have the best sex!

    Posted by: BrokebackBob | Nov 8, 2012 3:52:13 AM


  24. Diogenes Arktos:
    Can you tell which state doesn't have the "winner takes all" system? Certainly not Florida. If it is true, we won't have the Bush vs Gore legal battle when there were 25 votes at stake instead of just one vote.
    The wiki says:
    While laws vary, most states, including Florida, award all electoral votes to the candidate for either office who receives a plurality of the state's popular vote.
    It doesn't say which states are the exceptions.
    Anyway, no matter what the rules are, Nate Silver should have got the number right if his model is 100% accurate.
    Luke and Bill here seem to imply that the Florida's result is still pending and the media assigned only a fraction of the votes to make up the 303 number which obviously is not going to happen.

    Posted by: simon | Nov 8, 2012 7:54:15 AM


  25. As an answer to Simon's question, Maine and Nebraska assign two electoral votes to the state-wide winner and the rest depend on who won the election in each congressional district in those states. It seems that in both states, the same candidate won in all of a given stete's districts, so a split has not been seen in practice.
    Source: http://archive.fairvote.org/e_college/me_ne.htm

    Simon's statement that "Luke and Bill here seem to imply that the Florida's result is still pending and the media assigned only a fraction of the votes to make up the 303 number which obviously is not going to happen," indicates a misunderstanding as to what we were saying. The 303 number is without Florida (the Florida vote is still pending although Romney has apparently conceded that Obama will win Florida). Until the vote is official or the outcome certain, the media is not assigning Florida's votes to either candidate. The sort of pre-election analysis that Nate Silver did, however, would formally split the vote, but purely for mathematical reasons. Basically, he's computing the distribution function for the vote - the probability of the electoral vote having some specific value - and that function is to a good approximation a normal distribution (a "bell-shaped curve") whose peak value is the sum of the means for each state. For Florida, because it is so close to a tie, the mean is approximate 14.5 (i.e., 29/2). If you want to see in detail why it works this way, do a google search for "central limit theorem" and "law of large numbers", but keep in mind that you will be lost if you haven't had a few years of college-level calculus so that, for example, you know what a Fourier transform is.

    Posted by: Bill | Nov 8, 2012 8:52:38 PM


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