Expected value is a concept in probability that helps us understand the average outcome of a random event over time. It is calculated by multiplying each possible outcome by its probability and then summing these products. For example, if you roll a die, the expected value of the roll is the average of all possible outcomes, which is 3.5. This idea is useful in various fields, such as gambling, finance, and decision-making. By knowing the expected value, you can make more informed choices. For instance, if a game has a higher expected value, it might be a better option to play compared to one with a lower expected value.