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2018 Senate · MT

Gravis Marketing · fieldwork ended 2018-10-25 (12 days before the election) · 782 respondents · Live Phone/Online Panel

The poll said

Democrat 48% · Republican 45%

D+3.0

The certified result

Democrat 50.33% · Republican 46.78%

D+3.6

The arithmetic

  1. Poll margin = 48 − 45 = 3.00
  2. Actual margin = 50.334 − 46.782 = 3.552
  3. Signed miss = 3.00 − (3.552) = -0.551
  4. Absolute miss = |-0.551| = 0.551

The poll overstated the Republican by 0.6 points and had the right leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 56546, race ID 110 (538 database).