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1998 Senate · IL

Market Shares Corp. · fieldwork ended 1998-10-19 (15 days before the election) · 1,099 respondents · Live Phone

The poll said

Democrat 38% · Republican 48%

R+10.0

The certified result

Democrat 47.44% · Republican 50.35%

R+2.9

The arithmetic

  1. Poll margin = 38 − 48 = -10.00
  2. Actual margin = 47.444 − 50.347 = -2.903
  3. Signed miss = -10.00 − (-2.903) = -7.097
  4. Absolute miss = |-7.097| = 7.097

The poll overstated the Republican by 7.1 points and had the right leader.

Where these numbers come from

Poll and result: 538 raw_polls.csv. Poll ID 26083, race ID 1728 (538 database).