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2018 Governor · IA

Change Research · fieldwork ended 2018-11-03 (3 days before the election) · 961 respondents · Text-to-Web/Online Ad

The poll said

Democrat 49% · Republican 46%

D+3.0

The certified result

Democrat 47.53% · Republican 50.26%

R+2.7

The arithmetic

  1. Poll margin = 49 − 46 = 3.00
  2. Actual margin = 47.527 − 50.260 = -2.733
  3. Signed miss = 3.00 − (-2.733) = 5.733
  4. Absolute miss = |5.733| = 5.733

The poll overstated the Democrat by 5.7 points and had the wrong leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 56796, race ID 143 (538 database).