Answer
In a probability experiment there are some possible values for the variable X. If, the experiment is repeated a large number of times, we expect an average value for the variable X. This value is called the mean (or expected value).
Work Step by Step
Let $μ_X$ be the mean (or expected value).
Let $x_1$ be the value for X obtained in the first experiment.
Let $x_2$ be the value for X obtained in the second experiment.
.
.
.
And so on.
Let $n$ be a large number.
If you repeat the experiment n times, it is expected that:
$\frac{Σx_i}{n}=\frac{x_1+x_2+...+x_n}{n}\approxμ_X$
