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2012 President · SD

Nielson Brothers Polling · fieldwork ended 2012-10-30 (7 days before the election) · 671 respondents · IVR

The poll said

Democrat 42% · Republican 50%

R+8.0

The certified result

Democrat 39.87% · Republican 57.89%

R+18.0

The arithmetic

  1. Poll margin = 42 − 50 = -8.00
  2. Actual margin = 39.866 − 57.889 = -18.023
  3. Signed miss = -8.00 − (-18.023) = 10.023
  4. Absolute miss = |10.023| = 10.023

The poll overstated the Democrat by 10.0 points and had the right leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 30615, race ID 694 (538 database).