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2004 Senate · IL

SurveyUSA · fieldwork ended 2004-10-28 (5 days before the election) · 655 respondents · IVR

The poll said

Democrat 66% · Republican 27%

D+39.0

The certified result

Democrat 69.97% · Republican 27.05%

D+42.9

The arithmetic

  1. Poll margin = 66 − 27 = 39.00
  2. Actual margin = 69.969 − 27.048 = 42.921
  3. Signed miss = 39.00 − (42.921) = -3.920
  4. Absolute miss = |-3.920| = 3.920

The poll overstated the Republican by 3.9 points and had the right leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 4385, race ID 1625 (538 database).