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2010 Senate · MA

InsiderAdvantage · fieldwork ended 2010-01-17 (2 days before the election) · 804 respondents · IVR

The poll said

Democrat 43.1% · Republican 52.2%

R+9.1

The certified result

Democrat 47.09% · Republican 51.86%

R+4.8

The arithmetic

  1. Poll margin = 43.1 − 52.2 = -9.10
  2. Actual margin = 47.095 − 51.860 = -4.765
  3. Signed miss = -9.10 − (-4.765) = -4.336
  4. Absolute miss = |-4.336| = 4.336

The poll overstated the Republican by 4.3 points and had the right leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 63679, race ID 1526 (538 database).