Mathematics 9709 · AS & A Level · Continuous random variables

Continuous random variables — practice question

Let the random variable $X$ have probability density function given by $$f(x)=\begin{cases}\frac{3}{16}(4x-x^2), & 2 \leq x \leq 4, \\ 0, & \text{otherwise}.\end{cases}$$
(a)[3]

Show that $\mathrm{E}(X)=\frac{11}{4}$.

(b)[3]

Find $\mathrm{Var}(X)$.

(c)[3]

If the median of $X$ is $m$, find $\mathrm{P}(m<X<3)$.

Worked solution & mark scheme

This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: An attempt to integrate $x f(x)$ is made

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