Variance of transformed variable

Questions that ask to find the variance of a transformation of X, such as Var(aX + b) or Var(g(X)), requiring use of variance transformation rules.

2 questions

CAIE Further Paper 4 2024 June Q7
7 The continuous random variable \(X\) has probability density function f given by $$f ( x ) = \left\{ \begin{array} { c c } \frac { x } { 4 } \left( 4 - x ^ { 2 } \right) & 0 \leqslant x \leqslant 2
0 & \text { otherwise } \end{array} \right.$$
  1. Find \(\operatorname { Var } ( \sqrt { X } )\).
    The continuous random variable \(Y\) is defined by \(Y = X ^ { 2 }\).
  2. Find the probability density function of \(Y\).
  3. Find the exact value of the median of \(Y\).
    If you use the following page to complete the answer to any question, the question number must be clearly shown.
AQA Further AS Paper 2 Statistics 2024 June Q6
2 marks
6 The continuous random variable \(X\) has probability density function $$f ( x ) = \begin{cases} \frac { 3 x } { 44 } + \frac { 1 } { 22 } & 1 \leq x \leq 5
0 & \text { otherwise } \end{cases}$$ 6
  1. Find \(\mathrm { P } ( X > 2 )\)
    [0pt] [2 marks]
    6
  2. Find the upper quartile of \(X\) Give your answer to two decimal places.
    6
  3. Find \(\operatorname { Var } \left( 44 X ^ { - 3 } \right)\) Give your answer to three decimal places.