Mathematics 9709 · AS & A Level · Continuous random variables

Continuous random variables — practice question

The random variable $X$ is described by the probability density function $f$, where $f(x) = \begin{cases} ax - x^3, & 0 \leq x \leq \sqrt{2}, \\ 0, & \text{otherwise}, \end{cases}$ and $a$ is a constant.
(a)[3]

Show, by calculation, that $a = 2$.

(b)[4]

Find the median value of $X$.

(c)[3]

Find the exact value for $\text{E}(X)$.

Worked solution & mark scheme

This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: Form the equation $\int_0^{\sqrt2}(ax-x^3)\,dx=1$

  • Full mark scheme, point by point
  • Step-by-step worked solution
  • Write your answer & get it marked instantly by AI