Calling the Race

The big winner from the US Presidential election has been Nate Silver and his 538 blog. On the eve of the election, Silver had calculated the following probabilities from polling data:

Silver also has a fascinating analysis of which polls were accurate, and which weren’t. In particular, polls based on calling landline telephones tended to seriously underestimate the Democrat vote. Voters without landlines are more likely to be young, urban, Black, Hispanic, strapped for cash, or some combination of the five, and all five categories are more likely to vote Democrat. There are lessons here for pollsters in other countries.

The following simple NetLogo simulation model (click on the image to run it) re-rolls Silver’s electoral dice, giving alternative outcomes – exactly the kind of simulation Silver actually did to support his 90% prediction of an Obama win:

Silver appears to take a Bayesian approach to statistics. A Bayesian has been described as “one who, vaguely expecting a horse, and catching a glimpse of a donkey, strongly believes he has seen a mule.” The legendary XKCD summarises the perspective quite elegantly:

– Tony

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3 Responses to Calling the Race

  1. igorupdate says:

    Tony, I couldn’t get the sim to run!!! So disappointed!
    But I go the cartoon to make my diaphragm jiggle!

  2. Tony says:

    The sim was tested on Firefox and IE. What goes wrong?

    It requires Java, so there may be a problem with your Java settings.

  3. Tony says:

    Here is another simulator which looks much nicer, although it doesn’t use Silver’s probabilities: http://www.270towin.com/simulation/

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