3 ms·

I think Nate is pretty sharp -- but I don't trust the people who answer polls. Who has time to pick up the phone? Most of the time it's some spammer. And if you

I think Nate is pretty sharp -- but I don't trust the people who answer polls. Who has time to pick up the phone? Most of the time it's some spammer. And if you do answer, why tell the truth about your vote?

scarmig 6y ago
That's also true of every election in recent history, and yet polls still historically have had predictive power. Even shy Tory stories are perennial fixtures in the poll criticism genre; perhaps it could exist as a stronger effect this year, but as yet there's no evidence that it is.
saeranv 6y ago
538 does rank pollsters based on "historical accuracy and methodology"[1], which are then weighted accordingly in their prediction model. And Nate and Elliot Morris (from the economist) have talked about how polling error tends to be normally distributed, so using multiple pollsters with different biases could correct for polling error. Pollsters are picking representative samples and weighting it to reflect the population, so it's not like they're just counting on who picks up their phone (and phone calls aren't the only way to poll anymore anyway). As I recall, in 2016 the pollsters did oversample college-educated white voters, which is what gave Clinton her misleading lead. This apparently has been fixed. There's also the fact that any demographic under or oversampling should be accounted for in the uncertainty range produced by the prediction. I haven't been able to find decent write-ups of this particular part of model forecasting, but from what I've been able to piece together : I believe they quantify the uncertainty of their presidential predictions by building logistic regressions of the output based on highly-correlated predictor data (i.e demographic information, GDP) and then simulating thousands of possible scenarios where demographics trend differently. I don't exactly know how these simulations are set up (I would love to know though). And presumably this is updated in a bayesian matter everytime they get more input data, so the prior probabilities will have an impact on the posterior. If anyone has a different or more detailed idea of how this is done, let me know. In fact, here's the actual code for Elliot Morris' forecasting model: https://github.com/TheEconomist/us-potus-model https://github.com/TheEconomist/us-potus-model if anyone can figure it out better then me. [1] https://projects.fivethirtyeight.com/pollster-ratings/ https://projects.fivethirtyeight.com/pollster-ratings/ [2] https://www.vox.com/21538156/biden-polls-lead-election-trump-2020-2016 https://www.vox.com/21538156/biden-polls-lead-election-trump...
cameldrv 6y ago
I think that the point is that both the pollsters and Nate are looking at how various polling methodologies correlate to actual past election results. The raw numbers from a poll are no good though, because you have a biased sample. The people who answer the survey are not representative of the people who show up to vote. They use the actual election results to calibrate the correction for this. As long as these relationships stay stable, polls should be pretty accurate. In my understanding, the biggest problem in 2016 was that the polls were undercorrecting for the difference between college educated voters vs. not college educated voters. Historically, this made less of a difference than other factors in voting behavior, so it had less impact in the weighting model. In 2016, it had a lot of impact, and college educated voters were more likely to answer the survey, so their tendency to vote Hillary was overrepresented in the polls. That said, the polls were off by less than 2% nationally. Perhaps that's not a great result, but it's not as if they were wildly wrong, it was just a close election. Unfortunately this election is also somewhat close this year, and voting behavior is going to be different with the pandemic, mail in voting, etc. I think it's very hard to reliably call Pennsylvania.
smitty1e 6y ago
Trump in 2016, and again in 2020 is running a disintermediation campaign and going straight to the voters with the rallies. If again effective, perhaps the teachers will return to school and learn something.
dave333 6y ago
This what scares me about the polls - that they don't account for Trump supporters being less truthful than the rest of us. Just look at Trump - he hasn't said anything true for years.

scarmig 6y ago

That's also true of every election in recent history, and yet polls still historically have had predictive power. Even shy Tory stories are perennial fixtures in the poll criticism genre; perhaps it could exist as a stronger effect this year, but as yet there's no evidence that it is.

saeranv 6y ago

538 does rank pollsters based on "historical accuracy and methodology"[1], which are then weighted accordingly in their prediction model. And Nate and Elliot Morris (from the economist) have talked about how polling error tends to be normally distributed, so using multiple pollsters with different biases could correct for polling error. Pollsters are picking representative samples and weighting it to reflect the population, so it's not like they're just counting on who picks up their phone (and phone calls aren't the only way to poll anymore anyway). As I recall, in 2016 the pollsters did oversample college-educated white voters, which is what gave Clinton her misleading lead. This apparently has been fixed. There's also the fact that any demographic under or oversampling should be accounted for in the uncertainty range produced by the prediction. I haven't been able to find decent write-ups of this particular part of model forecasting, but from what I've been able to piece together : I believe they quantify the uncertainty of their presidential predictions by building logistic regressions of the output based on highly-correlated predictor data (i.e demographic information, GDP) and then simulating thousands of possible scenarios where demographics trend differently. I don't exactly know how these simulations are set up (I would love to know though). And presumably this is updated in a bayesian matter everytime they get more input data, so the prior probabilities will have an impact on the posterior. If anyone has a different or more detailed idea of how this is done, let me know. In fact, here's the actual code for Elliot Morris' forecasting model: https://github.com/TheEconomist/us-potus-model https://github.com/TheEconomist/us-potus-model if anyone can figure it out better then me. [1] https://projects.fivethirtyeight.com/pollster-ratings/ https://projects.fivethirtyeight.com/pollster-ratings/ [2] https://www.vox.com/21538156/biden-polls-lead-election-trump-2020-2016 https://www.vox.com/21538156/biden-polls-lead-election-trump...

cameldrv 6y ago

I think that the point is that both the pollsters and Nate are looking at how various polling methodologies correlate to actual past election results. The raw numbers from a poll are no good though, because you have a biased sample. The people who answer the survey are not representative of the people who show up to vote. They use the actual election results to calibrate the correction for this. As long as these relationships stay stable, polls should be pretty accurate. In my understanding, the biggest problem in 2016 was that the polls were undercorrecting for the difference between college educated voters vs. not college educated voters. Historically, this made less of a difference than other factors in voting behavior, so it had less impact in the weighting model. In 2016, it had a lot of impact, and college educated voters were more likely to answer the survey, so their tendency to vote Hillary was overrepresented in the polls. That said, the polls were off by less than 2% nationally. Perhaps that's not a great result, but it's not as if they were wildly wrong, it was just a close election. Unfortunately this election is also somewhat close this year, and voting behavior is going to be different with the pandemic, mail in voting, etc. I think it's very hard to reliably call Pennsylvania.

smitty1e 6y ago

Trump in 2016, and again in 2020 is running a disintermediation campaign and going straight to the voters with the rallies. If again effective, perhaps the teachers will return to school and learn something.

dave333 6y ago

This what scares me about the polls - that they don't account for Trump supporters being less truthful than the rest of us. Just look at Trump - he hasn't said anything true for years.