Proofiness and elections

I am enjoying Charles Seife’s Proofiness, but have to point out what I think is a flaw.  A major part of the book addresses errors in elections and election polls, and Seife presents a detailed analysis of two contested elections: Franken vs. Coleman in Minnesota and Gore vs. Bush in Florida.

In both cases the margin of victory was (much) smaller than the margin of error, and Seife concludes that the result should be considered a tie.  He points out:

“...both states, by coincidence, happen to break a tie in exactly the same way.  In the case of a tie vote, the winner shall be determined by lot.  In other words, flip a coin.  It’s hard to swallow, but the 2008 Minnesota Senate race and, even more startling, the 2000 presidential election should have been settled with the flip of a coin.”

So far, I agree, but Seife implies that this solution would avoid the legal manipulations that follow close elections (which he describes in entertaining detail, including a contested ballot in Minnesota full of write-in votes for “Lizard People”).

But Seife doesn’t solve the problem; he only moves it.  Instead of two outcomes (A wins and B wins) there are three (A wins, statistical tie, B wins), but the lines between outcomes are just as sharp, so any election that approaches them will be just as sharply contested.

As always, the correct solution is easy if you just apply Bayesian statistics.  In order to compute the margin of error, we need a model of the error process (for example, there is a chance that any vote will be lost, and a chance that any vote will be double counted).  With a model like that, we can use the observed vote count to compute the probability that either candidate received more votes.  Then we toss a biased coin, with the computed probability, to determine the winner.

For example, the final count in the 2008 Minnesota Senate race was 1,212,629 votes for Franken and 1,212,317 votes for Coleman.  But the actual number of votes cast for each candidate could easily be 1000 more or less than the count, so it is possible that Coleman actually received more votes; if we do the math, we might find that the probability is 30%.  In that case, I suggest, we should choose a random number between 1 and 100, and if it is less than 30, Coleman wins.

This system has a few nice properties: it solves the problem Seife calls “disestimation,” which is the tendency to pretend that measurements are more precise than they are.  And it is fair in the sense that the probability of winning equals the probability of receiving more votes.

There are drawbacks.  One is that it, in order to model the error process, we have to acknowledge that there are errors, which is unpalatable.  The other is that it is possible for a candidate with a higher vote count to lose.  That outcome would be strange, but certainly no stranger than the result of the 2000 presidential election.
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If you find this sort of thing interesting, you might like my free statistics textbook, Think Stats. You can download it or read it at thinkstats.com.