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2008 President · IA

SurveyUSA · fieldwork ended 2008-10-28 (7 days before the election) · 658 respondents · IVR

The poll said

Democrat 55% · Republican 40%

D+15.0

The certified result

Democrat 53.93% · Republican 44.39%

D+9.5

The arithmetic

  1. Poll margin = 55 − 40 = 15.00
  2. Actual margin = 53.928 − 44.393 = 9.535
  3. Signed miss = 15.00 − (9.535) = 5.465
  4. Absolute miss = |5.465| = 5.465

The poll overstated the Democrat by 5.5 points and had the right leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 16572, race ID 716 (538 database).