A gambler's fallacy is the incorrect belief that the probability of an event will change due to the outcome of a previously completed event. For example, before two coins are flipped, the odds of flipping two heads in a row are 1 out of 4 or 25%. If the first coin flipped lands heads, the belief that a second flip only has a 25% chance of landing heads again is a gambler's fallacy. The reality is that the probability of flipping heads a second time is actually 50% because the odds of a coin flip do not change due to the results of a previous flip.