Math
Random variables.
Definition
A variable whose value is determined by the outcome of a random process. Discrete random variables take countable values (like number of heads), while continuous random variables take any value in an interval (like height).
Examples
Real-world.
- 1 X = number of heads when flipping a coin 10 times (discrete)
- 2 X = the exact time a bus arrives (continuous)
- 3 X = the sum of two rolled dice (discrete, values 2-12)
Key Fact
E(X) = Σ[x · P(x)] for discrete; Var(X) = E(X²) - [E(X)]²