US Presidential Election 2004
After a long and sometimes unpleasant campaign, the US Presidential Election for 2004 took place on the 2nd of November. Polls opened in New York at 06:00, and closed in Hawaii at 20:00 local time. The pre-election surveys by various organizations indicated it was a very close battle, with some giving the edge to President Bush and others to Senator Kerry. Both campaigns were intensely focused on battleground states, the must-win states that included Florida, Pennsylvania, Ohio and a few others with smaller numbers of electoral votes. In the end, the question came down to which candidate would take Ohio, and it was Bush, with a small but ultimately undisputed majority (some people still worry that the new computerized balloting is vulnerable to errors and even to hacking). Bush also had a substantial margin of some 2 or 3 million in the popular vote, and in at noon on 3 November, Kerry called Bush to congratulate him on having won the election.
The formal prediction made before the election was that the period defined by the opening to closing of all polls in the US would show a departure from expectation. I should note that experience has indicated that political events typically do not yield notable deviations, but we want to learn what actually happens in different categories of events, and the methods we use require that we make a prediction of deviation -- even if we don't believe that will occur. See note below on Bayesian prediction.
The outcome of the formal analysis is a non-significant negative trend, with Chisquare of 68129 on 68400 df, which has a corresponding p-value of 0.768 and Z = -0.732.
It is interesting to look at a longer period around the formal segment of data. The next figure shows a few hours before and after, including the public concession speech by Kerry at 14:00 in Boston. This shows that except for a few hours at the beginning, the election period corresponded to a flat trace with no indication of anything but a random walk.
York Dobyns made a very specific prediction prior to the election that it would show a "flat" non-significan outcome (much as it in fact did). He proposes to do, when time allows, a Bayesian analysis to test this prediction.