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2017 Senate · AL

Gravis Marketing · fieldwork ended 2017-12-07 (5 days before the election) · 1,254 respondents · IVR/Online Panel

The poll said

Democrat 45% · Republican 49%

R+4.0

The certified result

Democrat 49.97% · Republican 48.34%

D+1.6

The arithmetic

  1. Poll margin = 45 − 49 = -4.00
  2. Actual margin = 49.966 − 48.340 = 1.626
  3. Signed miss = -4.00 − (1.626) = -5.626
  4. Absolute miss = |-5.626| = 5.626

The poll overstated the Republican by 5.6 points and had the wrong leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 50677, race ID 95 (538 database).