Probability is the measure of the likelihood that an event will occur. Probability is quantified as a number between 0 and 1 (where 0 indicates impossibility and 1 indicates certainty). The higher the probability of an event, the more certain that the event will occur. A simple example is the tossing of a fair (unbiased) coin. Since the coin is unbiased, the two outcomes («head» and “tail”) are both equally probable. Since no other outcomes are possible, the probability is 1/2 (or 50%), of either “head” or “tail”. In other words, the probability of “head” is 1 out of 2 outcomes; the probability of “tail” is also 1 out of 2 outcomes, expressed as 0.5.
