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2020 Senate · IA

Change Research · fieldwork ended 2020-10-31 (3 days before the election) · 1,084 respondents · Text-to-Web/Online Ad

The poll said

Democrat 48% · Republican 47%

D+1.0

The certified result

Democrat 45.15% · Republican 51.74%

R+6.6

The arithmetic

  1. Poll margin = 48 − 47 = 1.00
  2. Actual margin = 45.152 − 51.740 = -6.588
  3. Signed miss = 1.00 − (-6.588) = 7.588
  4. Absolute miss = |7.588| = 7.588

The poll overstated the Democrat by 7.6 points and had the wrong leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 72756, race ID 6272 (538 database).