We now know that the expected value of a random variable gives the center of the distribution of the variable. This idea is much more powerful than might first. The mean or expected value of X is defined by E(X) = sum xk p(xk). Interpretations: (i) The expected value measures the center of the probability distribution. Definition of expected value & calculating by hand and in Excel. Includes video. Find an expected value for a discrete random variable. Definition Let be a sample spacea probability measure defined on the events of and a random variable defined on. Probabilty Distribution for Number of Tattoos Each Student Has in a Population of Students Tattoos 0 1 2 3 4 Probability. If is a random variable and is another random variable such that where and are two constants, then the following holds: Inference About Regression Review: Slot games download free report it below without further comments. You may have seen this before referred to as a weighted average.