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2010 House · SD-1

Nielson Brothers Polling · fieldwork ended 2010-10-21 (12 days before the election) · 679 respondents · IVR

The poll said

Democrat 41.5% · Republican 40%

D+1.5

The certified result

Democrat 45.89% · Republican 48.12%

R+2.2

The arithmetic

  1. Poll margin = 41.5 − 40 = 1.50
  2. Actual margin = 45.891 − 48.119 = -2.228
  3. Signed miss = 1.50 − (-2.228) = 3.727
  4. Absolute miss = |3.727| = 3.727

The poll overstated the Democrat by 3.7 points and had the wrong leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 52085, race ID 4818 (538 database).