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2018 Senate · MT

Change Research · fieldwork ended 2018-11-03 (3 days before the election) · 879 respondents · Text-to-Web/Online Ad

The poll said

Democrat 46% · Republican 49%

R+3.0

The certified result

Democrat 50.33% · Republican 46.78%

D+3.6

The arithmetic

  1. Poll margin = 46 − 49 = -3.00
  2. Actual margin = 50.334 − 46.782 = 3.552
  3. Signed miss = -3.00 − (3.552) = -6.551
  4. Absolute miss = |-6.551| = 6.551

The poll overstated the Republican by 6.6 points and had the wrong leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 56762, race ID 110 (538 database).