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Wednesday, October 31, 2012

Right Wingers Don't Like Statistics

As mathematician Jason Rosenhouse points out when the data doesn't fit their ideology.  In the case of political election results, ignorance of statistics isn't a big deal.  The election results will soon be in and the winner will be known.


But what about statistics and juries?  What happens when jurors don't understand or ignore statistics?  The outcome is much more important.

Here's a delightful, old video of statistician Peter Donnelly on the subject:


Legal scholar Alan Dershowitz employed the prosecutor's fallacy (when an attorney misuses statistics, see Donnelly's slide at 17:00) when defending O.J. Simpson.  The prosecutors pointed out Simpson's history of battering his wife.  Dershowitz provided the statistic that only about 1 in 2,500 men who battered their wives went on to murder them.  Thus it seems unlikely that Simpson murdered his wife.  However, the relevant statistic is the probability that a battered wife who was murdered was murdered by her abuser.  That statistic is 9 in 10, which was not mentioned at the trial and leads to the understanding that it is very likely Simpson committed the crime.  Interestingly, only witnesses take an oath to tell the truth, not attorneys.

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