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2017 House · MT-1

Change Research · fieldwork ended 2017-05-22 (3 days before the election) · 1,888 respondents · Text-to-Web/Online Ad

The poll said

Democrat 44% · Republican 49%

R+5.0

The certified result

Democrat 44.37% · Republican 49.95%

R+5.6

The arithmetic

  1. Poll margin = 44 − 49 = -5.00
  2. Actual margin = 44.365 − 49.951 = -5.586
  3. Signed miss = -5.00 − (-5.586) = 0.586
  4. Absolute miss = |0.586| = 0.586

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

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 50592, race ID 1764 (538 database).