Discrete random variables · Year 13

In Year 13 you learn: discrete random variables.

A discrete random variable takes separate values, each with a probability. Its probability distribution lists the values and their probabilities. From it you can find the expected value (the long-run mean) and the variance.

Key facts

• The probabilities in a distribution add up to 1.
• E(aX + b) = aE(X) + b and Var(aX + b) = a² Var(X).
• The cumulative distribution function is F(x) = P(X ≤ x).