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2012 Senate · MA

University of Massachusetts Lowell Center for Public Opinion · fieldwork ended 2012-11-02 (4 days before the election) · 800 respondents · Live Phone

The poll said

Democrat 48% · Republican 49%

R+1.0

The certified result

Democrat 53.27% · Republican 45.79%

D+7.5

The arithmetic

  1. Poll margin = 48 − 49 = -1.00
  2. Actual margin = 53.274 − 45.790 = 7.484
  3. Signed miss = -1.00 − (7.484) = -8.484
  4. Absolute miss = |-8.484| = 8.484

The poll overstated the Republican by 8.5 points and had the wrong leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 30740, race ID 1482 (538 database).