Occasional reflections on Life, the World, and Mathematics

Archive for November, 2012

Screens or Weights?

I probably shouldn’t be spending so much of my time thinking about U.S. election polls: I have no special expertise, and everyone else in the country has lost interest by now. But I’ve just gotten some new information about a question that was puzzling me throughout the recent election campaign: What do pollsters mean when they refer to a likely voter screen? (more…)

Are you demographic?

As a sometime demographer myself, I am fascinated by the prominence of “demographics” as an explanatory concept in the recent presidential election, now already slipping away into hazy memory. Recent political journalism would barely stand without this conceptual crutch, as here and here and here. A bit more nuance here. Some pushback from the NY Times here.

The crassest expression of this concept came in an article yesterday by (formerly?) respected conservative journalist Michael Barone, explaining why he was no longer confident that Mitt Romney would win the election by a large margin. Recall that several days before the election, despite the contrary evidence of what tens of thousands of voters were actually telling pollsters, he predicted 315 electoral votes for Romney, saying “Fundamentals usually prevail in American elections. That’s bad news for Barack Obama.” In retrospect, he says,

I was wrong because the outcome of the election was not determined, as I thought it would be, by fundamentals…. I think fundamentals were trumped by mechanics and, to a lesser extent, by demographics.

(more…)

The Silver standard

Who speaks for statistics?Silver coins

Ace forensic psephologist Nate Silver has attracted quite a bit of attention lately, with his 4+-year-old blog devoted to his statistical model that is intended to provide a synoptic view of the entire range of public data to produce a single probabilistic prediction of the outcome. Now, there are some clear criticisms that could be made of his approach, and of his results — in particular, the obvious failure of his successive predictions to be martingales, as they would have to be if they were appropriately using all current information — but he has been remarkably clear and open about his procedures and principles, and his reasoning on matters large and small seems generally sound, if not necessarily compelling. It’s funny that his conclusions should arouse any controversy at all, given that they are hardly different (as Silver himself is quick to acknowledge) from the conclusions one would draw from a simplistic combination of poll results. His main contribution is in giving careful answers to the obvious critiques that could be proposed: What’s a reasonable estimate for the difference between state poll results and the actual election result? How correlated are polling errors? What’s the best way to average polls of varying qualities done over multiple days? And so on. In the end, the answer doesn’t differ much from what anyone with number sense would come up with in a few hours, but you don’t know that for sure until you do it. And Silver’s reputation derives from the sense and good care that he takes in posing these questions and resolving them.

(The failure of the martingale property is actually evidence of his honesty in following the model that he set up back in the spring. He clearly would have been capable of recognising the trends that other people can see in the predictions, and introducing an ad hoc correction. He didn’t do that.) (more…)

Evolution turns political

… followed by arithmetic

There are two general attitudes that a scientifically-minded educated person could take to the resurgence of anti-Darwinian politics in the US over the past few decades. 1) Children deserve to know the truth, as best as careful thinkers have been able to determine it. Parents have no right to withhold the truth. We need to break the cycle of ignorance. Disrespect for standards of science and objective truth in one area will undermine science universally, making it more difficult for our society to benefit, materially and intellectually, from scientific progress. 2) Evolution is a story. It is abstract. It is a belief system that lends itself at least as much to social and political abuse as an fundamentalist sect, so maybe we shouldn’t be pushing it too hard — particularly not when there’s a conflict with parental beliefs and values. There’s plenty of science to learn — even biology — that won’t run up against conflict with home values. Where it’s a problem, let’s leave these abstract matters for when they are older and more qualified to make their own value judgements. (Given the difficulty of US schools recruiting competent science teachers, we might also add the very real harm that is likely to be done by teachers who genuinely don’t understand evolution, teaching corrupted or incomprehensible versions of the key ideas.) (more…)

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