Earlier quoted context omitted.
538 analyzed the various polls--and corrected for their methodologies and predictive power--just fine! A sibling comment brings up a batter, and I think that's a great analogy. A good batter has a batting average of, say 0.273. Nobody is shocked when they hit the ball! 538 gave a similar chance to Trump. He hit the ball.
Yes and no. 538 published an article after the election explaining that there were in fact systemic errors in the models; the result wasn't just random probability within models that were otherwise correct: https://fivethirtyeight.com/features/the-polls-missed-trump-... > While the errors were nationwide, they were spread unevenly. The more whites without college degrees were in a state, the more Trump outperformed h…
Of course, the polls themselves also acknowledge the chance of a systemic error. They're reported similar to +/- 2% 19 times out of 20. They make no claim that the 19/20 of multiple polls are not correlated.