Nick Berry at Datagenetics says that the 13th day of the month is more likely to be a Friday than any other day of the week. How could that be? Well, this is the guy who taught us how to win at Hangman and Battleship, how to defeat a monster with math, and other useful stuff, so you know there’s an explanation. Darned if I can condense it, though. The chart above should tell you it’s true, but you’ll have to go to Datagenetics to see why.
Oh look! We have a Friday the 13th coming up next month! By then, you’ll be able to explain all this to your family and friends and really impress them.
That chart is a classic case of "extremely truncated bottom" (that I learned in school with the help of the book "How to Lie with Statistics"). If you look closely, it occurs 688 times over 400 years as opposed to 684 times for Saturday the 13th, a difference of 4 times, or ONCE every hundred years, also known as "statistically irrelevant". And remember kids, Irrelevant Never Forgets.
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The only issue I took with the article is that Mr. Berry states that the Earth rotates around the sun. Actually the Earth rotates about its axis, and it revolves around the sun.
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