Wednesday, May 18, 2016

Nate Silver and predicting Trump

Nate Silver indulges in self-criticism over his website's underestimation of Donald Trump's electoral strength, How I Acted Like A Pundit And Screwed Up On Donald Trump Five Thirty Eight 05/18/2016.

I'm struck by the resemblances of Silver's self-criticism to that made by The Young Turks in this segment, Nate Silver's Bias Exposed 05/10/2016:

Silver describes his key point as follows:

The big mistake is a curious one for a website that focuses on statistics. Unlike virtually every other forecast we publish at FiveThirtyEight — including the primary and caucus projections I just mentioned — our early estimates of Trump’s chances weren’t based on a statistical model. Instead, they were what we sometimes called ”subjective odds” — which is to say, educated guesses. In other words, we were basically acting like pundits, but attaching numbers to our estimates. And we succumbed to some of the same biases that pundits often suffer, such as not changing our minds quickly enough in the face of new evidence. Without a model as a fortification, we found ourselves rambling around the countryside like all the other pundit-barbarians, randomly setting fire to things. .../

Without having a model, I found, I was subject to a lot of the same biases as the pundits I usually criticize. In particular, I got anchored on my initial forecast and was slow to update my priors in the face of new data. And I found myself selectively interpreting the evidence and engaging in some lazy reasoning.6

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