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2018 House · IA-1

The New York Times/Siena College · fieldwork ended 2018-10-30 (7 days before the election) · 452 respondents · Live Phone

The poll said

Democrat 45.69% · Republican 39.18%

D+6.5

The certified result

Democrat 50.96% · Republican 45.91%

D+5.1

The arithmetic

  1. Poll margin = 45.69 − 39.18 = 6.51
  2. Actual margin = 50.964 − 45.907 = 5.057
  3. Signed miss = 6.51 − (5.057) = 1.454
  4. Absolute miss = |1.454| = 1.454

The poll overstated the Democrat by 1.5 points and had the right leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 56582, race ID 297 (538 database).