Find the Expected Value, Variance and Standard Deviation of a Discrete Random Variable

A discrete random variable is one which may take on only a countable number of distinct values such as 0,1,2,3,4,........ Discrete random variables are usually (but not necessarily) counts. If a random variable can take only a finite number of distinct values, then it must be discrete.
A measure of spread for a distribution of a random variable that determines the degree to which the values of a random variable differ from the expected value.