In many problems, it is desirable to describe some feature of the random variable by mean of a single number that can be computed from its probability distribution. Few such numbers are mean, mode and median. In this section, we shall discuss mean only.
Let X be a random variable whose possible values x1, x2, ......,xn occur with probabilities p1, p2,... pn, respectively.
The mean of a random variable X is also called expectation of X, denoted by E(X).
E(X) = µ = \(\sum^n_{i=1}\) xiEi
= x1p1 + x2p2 +... + xnpn
Thus, the mean of X, denoted by p, is the weighted aver-age of the possible values of X, each value being weighted by its probability with which it occurs.
