The cumulative distribution function $F(x)$ for a discrete random variable $X$ is given by $F(1) = 0.2$, $F(2) = 0.7$, and $F(3) = 1$. Find $P(X=2)$.
Mark scheme and worked answer
- M1 for knowing the relationship $P(X=2) = F(2) - F(1)$.
- M1 for substituting the values: $0.7 - 0.2$.
- A1 for stating the probability is $0.5$.