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2020 Senate · IA

Monmouth University Polling Institute · fieldwork ended 2020-10-17 (17 days before the election) · 501 respondents · Live Phone

The poll said

Democrat 51% · Republican 45%

D+6.0

The certified result

Democrat 45.15% · Republican 51.74%

R+6.6

The arithmetic

  1. Poll margin = 51 − 45 = 6.00
  2. Actual margin = 45.152 − 51.740 = -6.588
  3. Signed miss = 6.00 − (-6.588) = 12.588
  4. Absolute miss = |12.588| = 12.588

The poll overstated the Democrat by 12.6 points and had the wrong leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 71548, race ID 6272 (538 database).