> It does not address the possibility that there are systematic methodological shortcomings in the polls.
Yes, it does. FiveThirtyEight's modeling includes sources of uncertainty beyond just the margin of sampling error of the individual polls.
They've tallied up how much the polling consensus erred for past elections, and have found that while it is not consistent which direction the polling consensus will err for a give election cycle, it is possible to quantify what is a typical size of polling error. Or to put it another way, which methodological shortcomings matter changes from one election to the next, but that doesn't stop you from estimating how big an effect it is likely to have.
Assuming that the polls are likely to be collectively wrong by some amount is why the FiveThirtyEight forecast's probability distribution is so wide, with their 80% confidence interval for Trump's electoral college vote total currently spanning roughly 120 to 280.
(They also include uncertainty factors for how much the true state of the electorate's opinions could shift between now and election day, but those factors are fading out of the forecast model as election day approaches.)
Thanks for the correction about 538's methodology. In that case, the "batting average" analogy isn't really a good one, because that implies random odds. When it comes to systemic errors, it's something that is unknown, but is theoretically knowable in advance. This election is so weird that I think there may be lots of systemic errors like that.
Yes, it does. FiveThirtyEight's modeling includes sources of uncertainty beyond just the margin of sampling error of the individual polls.
They've tallied up how much the polling consensus erred for past elections, and have found that while it is not consistent which direction the polling consensus will err for a give election cycle, it is possible to quantify what is a typical size of polling error. Or to put it another way, which methodological shortcomings matter changes from one election to the next, but that doesn't stop you from estimating how big an effect it is likely to have.
Assuming that the polls are likely to be collectively wrong by some amount is why the FiveThirtyEight forecast's probability distribution is so wide, with their 80% confidence interval for Trump's electoral college vote total currently spanning roughly 120 to 280.
(They also include uncertainty factors for how much the true state of the electorate's opinions could shift between now and election day, but those factors are fading out of the forecast model as election day approaches.)