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2017 Senate · AL

Change Research · fieldwork ended 2017-12-10 (2 days before the election) · 1,556 respondents · Text-to-Web/Online Ad

The poll said

Democrat 45% · Republican 51%

R+6.0

The certified result

Democrat 49.97% · Republican 48.34%

D+1.6

The arithmetic

  1. Poll margin = 45 − 51 = -6.00
  2. Actual margin = 49.966 − 48.340 = 1.626
  3. Signed miss = -6.00 − (1.626) = -7.626
  4. Absolute miss = |-7.626| = 7.626

The poll overstated the Republican by 7.6 points and had the wrong leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 50674, race ID 95 (538 database).