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2016 Senate · PA

Gravis Marketing · fieldwork ended 2016-10-27 (12 days before the election) · 3,217 respondents · IVR

The poll said

Democrat 45% · Republican 41%

D+4.0

The certified result

Democrat 47.34% · Republican 48.77%

R+1.4

The arithmetic

  1. Poll margin = 45 − 41 = 4.00
  2. Actual margin = 47.341 − 48.774 = -1.433
  3. Signed miss = 4.00 − (-1.433) = 5.432
  4. Absolute miss = |5.432| = 5.432

The poll overstated the Democrat by 5.4 points and had the wrong leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 47867, race ID 86 (538 database).