Wednesday, November 9, 2016

Polling error

Well, I assume I don't need to tell you that the polls missed it yesterday. While that is a fact, what people don't seem to realize is that they really didn't miss by that much. In fact, you'd have to say that if a miss like this didn't happen every 20 years or so, then the polls are being way too conservative.

That's what a confidence interval means. There's a probability that the result falls in a given range. There is a complementary probability that the result does not fall in that range. If you never miss, you're confidence interval is off.

It's true that Sam Wang's 99% prediction over at the Princeton Election Consortium was a bit nutty and several other estimators called him out on it. (To his credit, he discovered his error and not only admitted it, but published the details on election night). However, most had Hillary at around 80%, which means they would expect to be wrong once every five elections (or, 20 years). This was the year.

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