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2010 Senate · IL

YouGov · fieldwork ended 2010-10-27 (6 days before the election) · 672 respondents · Online Panel

The poll said

Democrat 48.5% · Republican 45.8%

D+2.7

The certified result

Democrat 46.42% · Republican 48.02%

R+1.6

The arithmetic

  1. Poll margin = 48.5 − 45.8 = 2.70
  2. Actual margin = 46.416 − 48.015 = -1.599
  3. Signed miss = 2.70 − (-1.599) = 4.299
  4. Absolute miss = |4.299| = 4.299

The poll overstated the Democrat by 4.3 points and had the wrong leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 32791, race ID 1518 (538 database).