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2018 Senate · AZ

The New York Times/Siena College · fieldwork ended 2018-10-17 (20 days before the election) · 606 respondents · Live Phone

The poll said

Democrat 45.86% · Republican 47.65%

R+1.8

The certified result

Democrat 49.96% · Republican 47.61%

D+2.3

The arithmetic

  1. Poll margin = 45.86 − 47.65 = -1.79
  2. Actual margin = 49.956 − 47.611 = 2.345
  3. Signed miss = -1.79 − (2.345) = -4.134
  4. Absolute miss = |-4.134| = 4.134

The poll overstated the Republican by 4.1 points and had the wrong leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 56263, race ID 96 (538 database).