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2010 House · CA-20

SurveyUSA · fieldwork ended 2010-10-23 (10 days before the election) · 601 respondents · IVR

The poll said

Democrat 42% · Republican 52%

R+10.0

The certified result

Democrat 51.70% · Republican 48.30%

D+3.4

The arithmetic

  1. Poll margin = 42 − 52 = -10.00
  2. Actual margin = 51.705 − 48.295 = 3.410
  3. Signed miss = -10.00 − (3.410) = -13.410
  4. Absolute miss = |-13.410| = 13.410

The poll overstated the Republican by 13.4 points and had the wrong leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 51683, race ID 4500 (538 database).