# Guessing heads or tails isn't really a 50-50 game: study

Tossing a coin to settle an argument? Your chances of winning are not exactly 50-50!

If a coin is flipped with its heads side facing up, it will land the same way 51 out of 100 times, a Stanford researcher has claimed.

According to math professor Persi Diaconis, the probability of flipping a coin and guessing which side lands up correctly is not really 50-50.

He claims that a natural bias occurs when coins are flipped, which results in the side that was originally facing up returning to that same position 51 per cent of the time, a media report said.

Diaconis came to this conclusion after determining that no matter how hard a coin is flipped, the side that started up will spend more time facing up most of the time.

One way of thinking about this, as noted in an article from Coding Wheel, is to look at the ratio of even and odd numbers starting from one.

What you'll discover is that no matter what number you stop at, there will never be more even numbers than odd numbers in that sequence, the paper said.

The coin flips work in much the same way.

Diaconis first realised that coin flips were not random after he and his colleagues managed to rig a coin-flipping machine to get a coin to land heads every time.

He and his team then asked humans subjects do the same thing over and over, recording the results with a high speed camera. Though the results were a little more random, they still ended up with the 51-49 per cent margin.

Diaconis noted that the randomness is attributed to the fact that when humans flip coins, there are a number of different motions the coin is likely to make.

For instance, he showed how coins don't just move end to end, but also in a circular motion, like a tossed pizza.

... contd.