Monday, January 21, 2008

New Hampshire Recount: Statistical oddity

The New Hampshire primary vote recount is generating some interesting and unexpected results. The county that has been recounted so far shows wide differences between the vote and recount only in three precincts, in which there clearly were either malfunctions or manipulations of the voting machines. Overall, the recount does not affect the results on the Democratic side.

However, the distribution of differences between vote and recount (the errors) by precinct size is extremely intersting. As expected, the errors are smallest for the smallest precincts. If there are fewer votes to count, counting errors will of course be smaller. The spike in errors, however, is clearly in the mid-range of precinct sizes. The largest precincts, where we would expect to see the largest errors, actually have smaller errors.

In fact, it looks like there is an "expected" distribution of errors near the bottom of the graph, that slowly increases from small to large precincts. But in the region between 1000 and 2500 total votes (x axis), there seems to be a "hill" of unexpected results above the expected line (and the three outliers further above). This is a very unexpected pattern, and I am really not sure how to explain it right now.

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