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2018 House · PA-18

Emerson College · fieldwork ended 2018-03-02 (11 days before the election) · 474 respondents · IVR/Online Panel

The poll said

Democrat 48% · Republican 45%

D+3.0

The certified result

Democrat 49.86% · Republican 49.53%

D+0.3

The arithmetic

  1. Poll margin = 48 − 45 = 3.00
  2. Actual margin = 49.863 − 49.533 = 0.330
  3. Signed miss = 3.00 − (0.330) = 2.670
  4. Absolute miss = |2.670| = 2.670

The poll overstated the Democrat by 2.7 points and had the right leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 51025, race ID 1759 (538 database).