Question

When a penny made before 1982, is tossed up into the air the probability of landing tails up is pretty close to 0.500 ( 50% chance); however, if the penny is set spinning on a flat smooth horizontal surface, it is more than 80% likely to land tails up. Explain.

Answer 1

Spinning a coin on its edge on a table gives biased results due to uneven distribution of weight (especially on the old pennies). Again, the location of the coin's center of gravity makes a difference leading to tails more often than heads. Indeed, a spinning penny will land tails about 80 percent of the time. The spinning coin tends to fall toward the heavier side more often, leading to a pronounced number of extra “tails” results when it finally comes to rest.