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2018 Senate · AZ

Ipsos · fieldwork ended 2018-10-21 (16 days before the election) · 799 respondents · Online Panel/Probability Panel

The poll said

Democrat 46% · Republican 48%

R+2.0

The certified result

Democrat 49.96% · Republican 47.61%

D+2.3

The arithmetic

  1. Poll margin = 46 − 48 = -2.00
  2. Actual margin = 49.956 − 47.611 = 2.345
  3. Signed miss = -2.00 − (2.345) = -4.344
  4. Absolute miss = |-4.344| = 4.344

The poll overstated the Republican by 4.3 points and had the wrong leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 56586, race ID 96 (538 database).