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2008 Senate · IA

Scott Rasmussen (Rasmussen Reports) · fieldwork ended 2008-10-23 (12 days before the election) · 500 respondents · IVR

The poll said

Democrat 57% · Republican 41%

D+16.0

The certified result

Democrat 62.66% · Republican 37.26%

D+25.4

The arithmetic

  1. Poll margin = 57 − 41 = 16.00
  2. Actual margin = 62.656 − 37.261 = 25.395
  3. Signed miss = 16.00 − (25.395) = -9.395
  4. Absolute miss = |-9.395| = 9.395

The poll overstated the Republican by 9.4 points and had the right leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 16701, race ID 1554 (538 database).