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2018 Senate · MT

Trafalgar Group · fieldwork ended 2018-11-04 (2 days before the election) · 953 respondents · IVR/Email · partisan sponsor (REP)

The poll said

Democrat 50.1% · Republican 49%

D+1.1

The certified result

Democrat 50.33% · Republican 46.78%

D+3.6

The arithmetic

  1. Poll margin = 50.1 − 49 = 1.10
  2. Actual margin = 50.334 − 46.782 = 3.552
  3. Signed miss = 1.10 − (3.552) = -2.451
  4. Absolute miss = |-2.451| = 2.451

The poll overstated the Republican by 2.5 points and had the right leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 56816, race ID 110 (538 database).