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2008 House · IA-4

Tarrance Group · fieldwork ended 2008-10-22 (13 days before the election) · 300 respondents · Live Phone · partisan sponsor (REP)

The poll said

Democrat 34% · Republican 56%

R+22.0

The certified result

Democrat 39.43% · Republican 60.57%

R+21.1

The arithmetic

  1. Poll margin = 34 − 56 = -22.00
  2. Actual margin = 39.433 − 60.567 = -21.134
  3. Signed miss = -22.00 − (-21.134) = -0.866
  4. Absolute miss = |-0.866| = 0.866

The poll overstated the Republican by 0.9 points and had the right leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 64375, race ID 4185 (538 database).