Great story from NPR this week about the freakishly high number of American presidents who are left-handed. If you add in Obama/McCain (both of whom are lefties), five of the seven most recent U.S. presidents will be left-handed (as of January, 2009).
This is astounding when you consider that left-handers appear in the population at the rate of only about 10-15%. So, statistically, one would expect to have a left-handed president only about once per half-century.
What are the chances of getting five out of seven? Using binomial theorem, I calculated that whether you use 10% or 15% as a population parameter, or any number in between five left-handed presidents represents an outlier result more than five standard deviations from the expected mean (the mean being between 0.1*7 and 0.15*7, depending on which population parameter you pick i.e. about 1).
If we make a back-of-the-envelope analogy to normally distributed data, this means that the five-out-of-seven result falls outside the 99.9999% confidence interval associated with the baseline assumption that the handedness of an American president will reflect, without bias, the distribution of left-handers in the population from which the president is elected.
Clearly, this assumption is false (with “clearly” being defined as 99.9999% certainty). We must therefore answer the question: What is it about left-handers that makes them great presidents? On the NPR segment, Melissa Roth, author of The Left Stuff: How the Left-Handed Have Survived and Thrived in a Right-Handed World, offers a few fuzzy theories (left-handers are used to “standing out,” they see themselves as “different,” etc.) but they’re not particularly convincing.
Until the mystery is solved, Americans are doomed to live in a left-winged dictatorship.
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