Nate Silver, as all political junkies know, is the baseball stats guru who has morphed into a politics stats guru, running the blog 538.com, which now appears in the NY TIMES. [538 is the number of votes in the Electoral College, for overseas readers of this blog.] Silver achieved a brilliant forecasting record in 2008, successfully predicting the outcome in 49 of the 50 states and all 35 Senate races. Silver currently gives Obama a 75% chance of victory. Now, if my rudimentary grasp of statistics is correct, that means that roughly, over a long run, someone with Obama's current chances against his opponent should win three-quarters if the time, and someone with Romney's current chances against his opponent should win roughly one-quarter of the time. Right?
But in 2008, if my memory is correct, Silver was giving Obama and McCain winning chances in the various states in the range of 70-90%, not in the range 96-99%. Which means that either his statistical estimates were way off or 2008 was a really, really anomolous roll of the dice.
It is like adventures in white-water rafting or sky diving, which are billed as very dangerous, but in which virtually no one in fact ever dies.
It seems to me that if Silver is so often correct when he predicts presidential or senatorial races, then he should be assigning probabilities close to 1, not in the 75% range.
Am I missing something?