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Saturday, 17 September 2016

DEMOCRATS SHOULD PANIC---with a cameo about Bayesian forecaster Nate Silver


  Nate Silver, Author of The Signal and the Noise, and world famous Bayesian forecaster, His forecasts are usually amazing reliable since he refers to lots of background information in every state. See also this extract from my Personal History of Bayesian Statistics

   As reported by Charles Hogg, Nate Silver constructed a Bayesian model in 2008 to forecast the US general election results. Silver won fame for correctly predicting 49 of the 50 States, as well as every Senate race. That brought him a New York Times column and a much higher profile.
    In 2012, Nate’s continuing predictions that Obama would win earned him a curious backlash among pundits. While few of the criticisms had any merit, most were mathematically illiterate, indignantly mocking the idea that the race was anything other than a toss-up, Nevertheless, Nate confounded his critics by correctly predicting every single state.
    Charles Hogg was quick to advise us that Nate did strike lucky in Florida. Nate ‘called’ this state with a 50.3% Bayesian probability, essentially the proverbial coin-toss, a lucky gold coin perhaps. Way to go, Mr. Silver! Did you use a Jeffreys prior or a conjugate one?
    In his 2013 Kindle book The Signal and the Noise, which is about Bayesian prediction in general, Nate Silver assigned a prior probability of 1/20000 to the event that at least one plane is intentionally crashed into a Manhattan skyscraper on a given day. He then used Bayes theorem to update his prior probability to a probability of 0.385 that one plane crash is part of a Terrorist attack, and then to a probability of 99.99% that two plane crashes amount to a terrorist attack.
Nate Silver
    Maybe Nate should rename his book The Sound and the Fury, though a guy called Bill Faulkner once used a title like that. Calling it The Power and the Glory would, nowadays, be much too naff.

                                                           DEMOCRATS SHOULD PANIC

                 Hillary Clinton’s lead in the polls has been declining for several weeks, and now we’re at the point where it’s not much of a lead at all. National polls show Clinton only 1 or 2 percentage points ahead of Donald Trump, on average. And the state polling situation isn’t really any better for her. On Thursday alone, polls were released showing Clinton behind in Ohio, Iowa and Colorado — and with narrow, 3-point leads in Michigan and Virginia, two states once thought to be relatively safe for her.
It’s also become clearer that Clinton’s “bad weekend” — which included describing half of Trump supporters as a “basket of deplorables” on Friday, and a health scare (followed by news that she had been diagnosed with pneumonia) on Sunday — has affected the polls. Prior to the weekend, Clinton’s decline had appeared to be leveling off, with the race settling into a Clinton lead of 3 or 4 percentage points. But over the past seven days, Clinton’s win probability has declined from 70 percent to 60 percent in our polls-only forecast and by a similar amount, from 68 percent to 59 percent, in our polls-plus forecast.


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