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2010 Governor · IL

Public Policy Polling · fieldwork ended 2010-10-15 (18 days before the election) · 557 respondents · IVR

The poll said

Democrat 41% · Republican 42%

R+1.0

The certified result

Democrat 46.79% · Republican 45.94%

D+0.9

The arithmetic

  1. Poll margin = 41 − 42 = -1.00
  2. Actual margin = 46.789 − 45.935 = 0.854
  3. Signed miss = -1.00 − (0.854) = -1.853
  4. Absolute miss = |-1.853| = 1.853

The poll overstated the Republican by 1.9 points and had the wrong leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 32618, race ID 1285 (538 database).