Theoretically, the chances that heads or tails will come up when we toss a coin should be equal. That is, if we were to toss a coin 100 times, the outcomes for either heads or tails should be 50/50. However, scientists are now disputing that commonly held belief.
A study from the University of Amsterdam shows that coin tosses aren't immune to biases. PhD candidate František Bartoš, along with a team of researchers, have built upon the initial research done by Stanford University statistics professor Persi Diaconis and his team, which hypothesized that flipped coins generally fall on the same side they started. They coined a term (no pun intended) for this phenomenon, "same-side bias".
It is a vexing proposition but when Bartoš' team conducted a trial flipping coins from 46 different currencies for a total of 350,757 times, they found that the coins came up on the same side they started around 51% of the time. It's not a big difference, but it's not 50%.
Some factors lend further credence to the theory such as the coin flipper themselves. Depending on the way the coin is tossed, the chances that same-side bias will affect the outcome is higher. "Vigorously tossing" the coin is how the team described the manner the coins were tossed.
Perhaps, to remove all the biases, we should simply twirl the coin on its side. Of course, it's more difficult than simply flicking your thumb and catching the coin. Or, maybe tossing the coin sideways?
(Image credit: Andy Henderson/Unsplash)