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Ro-mentum watch: Karl Rove
by Sam Wang, November 1, 2012, 9:10am comment thread
In this year's race, national polls show a tie, while state polls show a decisive Obama advantage. Here I suggest that the difference may arise from the fact that the same systematic pollster errors can have different effects depending on whether they occur in national vs. state surveys. Based on past elections, national poll aggregates differ from election results by as much as 2.5%. During the same period, state-poll aggregation has been considerably more accurate. Even if state polls have the same accuracy as national polls, races at that level are usually decided by larger margins, leaving room for aggregation to remove the effect of the error. I suggest that the Meta-Analysis of state polls provides a more accurate poll-based prediction of next Tuesday's outcome than national polls.
In the Wall Street Journal, Karl Rove surprises basically nobody by predicting a Romney win. His reason? He cites a Romney lead in some national polls. This has become a rallying cry for the right. But is 'the math' correct?
Here at the Princeton Election Consortium, the Meta-Analysis of state polls points toward an Obama electoral victory. The median outcome is Obama 308, Romney 230 EV, with a Meta-Margin of Obama +2.4%+/-0.5%. To put it into plain English: If state polls are accurate on the whole, then Obama will win.
However, national polls give a different result. National polls since October 14th give a tied median, 'Obamney' +0.0 +/- 0.3% (n=44 polls, median +/- estimated SEM). Indeed, the discrepancy with the Meta-Analysis has been over 2.0% all season.
http://election.princeton.edu/romentum-rove-1nov2012.php
In this year's race, national polls show a tie, while state polls show a decisive Obama advantage. Here I suggest that the difference may arise from the fact that the same systematic pollster errors can have different effects depending on whether they occur in national vs. state surveys. Based on past elections, national poll aggregates differ from election results by as much as 2.5%. During the same period, state-poll aggregation has been considerably more accurate. Even if state polls have the same accuracy as national polls, races at that level are usually decided by larger margins, leaving room for aggregation to remove the effect of the error. I suggest that the Meta-Analysis of state polls provides a more accurate poll-based prediction of next Tuesday's outcome than national polls.
In the Wall Street Journal, Karl Rove surprises basically nobody by predicting a Romney win. His reason? He cites a Romney lead in some national polls. This has become a rallying cry for the right. But is 'the math' correct?
Here at the Princeton Election Consortium, the Meta-Analysis of state polls points toward an Obama electoral victory. The median outcome is Obama 308, Romney 230 EV, with a Meta-Margin of Obama +2.4%+/-0.5%. To put it into plain English: If state polls are accurate on the whole, then Obama will win.
However, national polls give a different result. National polls since October 14th give a tied median, 'Obamney' +0.0 +/- 0.3% (n=44 polls, median +/- estimated SEM). Indeed, the discrepancy with the Meta-Analysis has been over 2.0% all season.
http://election.princeton.edu/romentum-rove-1nov2012.php
