What is a random variable?
S is a sample space associated with the experiment E.
Random variable is then: Function X, which assigns a real number to every element s ∈ S.
X: S -> R
R is the set of all real numbers.
Example
Suppose we are tossing 2 coins.
Our sample space would be:
S = {HH, HT, TH, TT}
We can declare a random variable:
Number of heads
f(HH) = 2
f(HT) = 1
f(TH) = 1
f(TT) = 0