Random Variable

A random variable, as defined by J. Susan Milton and Jesse Arnold, is an assigned value, usually a real number, to all individual possible outcomes of an experiment. This mapping from outcome to value is a one-to-one relationship, meaning that for every experimental outcome, one and only numeric value is associated with it.

Take for example the tossing of two coins. The outcomes of such an experiment will have the following possibilities: heads, heads; heads, tails; tails, heads; and tails, tails. For this experiment, the random variable will map those categorical outcomes to numerical values, such as by letting the random variable X be the number of heads observed. Preserving the above order, the possible outcomes for X are 2, 1, 1, and 0. This particular ...