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If you roll that same die 10 times and you get a 6 each time, then we can say that your probability estimate was wrong. But that's what happened with the pollin
by hackinthebochs 6y ago
If you roll that same die 10 times and you get a 6 each time, then we can say that your probability estimate was wrong. But that's what happened with the polling of these states. The fact that the estimates consistently overestimated the Biden vote points towards a bias in the model used to estimate likely voters. If this were just a matter of the margin of error at work, each pull at the lever (each state) should be randomly distributed around the estimate. But that wasn't the case.
- whack 6y ago> If you roll that same die 10 times and you get a 6 each time, then we can say that your probability estimate was wrong. But that's what happened with the polling of these states. The 538 model is explicitly based on the assumption that the state-polling errors are correlated to one another to some extent. Ie, if Trump performs better-than-expected in OH, he will likely perform better-than-expected in FL as well. This is why they rated Trump's chances as being 0.1, not 0.1^8. Given how polling works, this is exactly the right assumption to make. Hence my earlier comment that if you want to evaluate the accuracy of 538 or any other model, you need to evaluate it across numerous different elections/events, over an extended period of time. Not a single day of elections in a single country.
- hackinthebochs 6y agoThis is kind of missing the point. The issue is the bias in the state-level polls. 538's model is to predict the winner of the election based on state polling data from other sources. The state level predictions are just averages of polls presumably weighted by quality. But this averaging cannot remove bias in the polls if that same bias is in many polls.