In this lesson, you will learn what an event is and the concept of the probability of an event. The probability of an event is defined as the ratio of how many times the event happens divided by the total number of trials in the experiment, as the number of trials approaches infinity. Because of this, the probability of an event doesn't have a meaning for only a few trials of an experiment. For example, the probability of getting heads or tails on the flip of a fair coin is 1/2, or 50%. However, for small number of trials I may get 3 heads in a row or 3 tails in a row. View More Lessons: http://www.MathAndScience.com