Mathematics 9709 · AS & A Level · Discrete random variables

Discrete random variables — practice question

The random variable $X$ may take the values $-2$, $2$ and $3$. You are told that $P(X = x) = k(x^2 - 1)$, where $k$ is a constant.

(a)[3]

Construct the probability distribution table for $X$, writing the probabilities as numerical fractions.

(b)[3]

Find the values of $\text{E}(X)$ and $\text{Var}(X)$.

Worked solution & mark scheme

This 6-mark question has a full step-by-step worked solution and mark scheme. One marking point: “From $3k+3k+8k=1$, deduce that $k=\frac{1}{14}$.” …