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2017 Senate · AL

JMC Analytics · fieldwork ended 2017-11-27 (15 days before the election) · 650 respondents · IVR

The poll said

Democrat 44% · Republican 49%

R+5.0

The certified result

Democrat 49.97% · Republican 48.34%

D+1.6

The arithmetic

  1. Poll margin = 44 − 49 = -5.00
  2. Actual margin = 49.966 − 48.340 = 1.626
  3. Signed miss = -5.00 − (1.626) = -6.626
  4. Absolute miss = |-6.626| = 6.626

The poll overstated the Republican by 6.6 points and had the wrong leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 50682, race ID 95 (538 database).