When the value of a variable is the outcome of a statistical experiment, that variable is a random variable. Suppose you flip a coin two times. This simple statistical experiment can have four possible outcomes: HH, HT, TH, and TT. Now, let the variable X represent the number of Heads that result from this experiment. The variable X can take on the values, 0, 1, or 2. In this example, X is a random variable because its value is determined by the outcome of a statistical experiment.