A variable, say XX, that can take certain values, each with a corresponding probability, is called a random variable; in the example above, the random variable was the sum of the two dice. If the poss...A variable, say XX, that can take certain values, each with a corresponding probability, is called a random variable; in the example above, the random variable was the sum of the two dice. If the possible values for X are \boldsymbol{_1,_2,_3,......._} then the expected value of the random variable is ()=∑=1()E(X)=∑i=1nxiP(xi) E(X)=\sum_{i=1}^n x_iP(x_i). The expected value is also called the mean.
