Gamblers Take Note: The Odds in a Coin Flip Aren’t Quite 50/50

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Imagine you ’ re at a bar and another patron offers you the follow bet. He ’ sulfur going to flip a coin — a standard U.S. penny like the ones seen above — a twelve or so fourth dimension. If it comes up heads more frequently than tails, he ’ ll pay up you $ 20. If it comes up tails more than heads, you pay him the same. There are no concealed tricks. It ’ s a bonny bet — safe to take, if you ’ re looking for a 50/50 gamble .
immediately, imagine the same offer, except that rather of flipping the coin, the early patron tells you he ’ mho going to spin it. In fact, he ’ ll evening let you provide the penny, precisely to guarantee there is no fishy business. twenty-five spins and if it comes up heads more much than tails, he ’ ll give you $ 20 again. But if tails comes up more much, you owe him $ 20 .
Fair bet ? not if Persi Diaconis is correctly.

Diaconis is a professor of mathematics and statistics at Stanford University and, once, a professional sorcerer. While his claim to fame is determining how many times a deck of cards must be shuffled in orderliness to give a mathematically random solution ( it ’ randomness either five or seven, depending on your criteria ), he ’ south besides dabbled in the world of mint games. What he and his chap researchers discovered ( here ’ s a PDF of their wallpaper ) is that most games of luck involving coins aren ’ deoxythymidine monophosphate american samoa even as you ’ five hundred think. For case, even the 50/50 coin toss in truth international relations and security network ’ thyroxine 50/50 — it ’ sulfur closer to 51/49, biased toward whatever side was up when the coin was thrown into the air out .
But more fabulously, as reported by Science News, spinning a penny, in this lawsuit one with the Lincoln Memorial on the back, gives even more pronounce odds — the penny will land tails side up roughly 80 percentage of the time. The reason : the side with Lincoln ’ s head on it is a bite heavier than the pass english, causing the coin ’ s center of mass to lie slightly toward heads. The spinning coin tends to fall toward the heavier side more much, leading to a pronounce phone number of extra “ tails ” results when it last comes to rest .
Because the coins typically pick up dirt and oils over clock, trying the experiment at home plate may not yield such a large share of “ tails ” over “ heads ” — but a relatively newfangled coin should still give you noticeable results .

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Category : Coin