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.

3 questions · Standard +0.7

5.03a Continuous random variables: pdf and cdf5.03b Solve problems: using pdf5.03f Relate pdf-cdf: medians and percentiles
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CAIE Further Paper 4 2024 June Q7
10 marks Challenging +1.2
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
11 marks Challenging +1.2
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.
Edexcel S2 2015 June Q6
11 marks Moderate -0.3
A continuous random variable \(X\) has probability density function f(\(x\)) where $$f(x) = \begin{cases} kx^n & 0 \leq x \leq 1 \\ 0 & \text{otherwise} \end{cases}$$ where \(k\) and \(n\) are positive integers.
  1. Find \(k\) in terms of \(n\). [3]
  2. Find E(\(X\)) in terms of \(n\). [3]
  3. Find E(\(X^2\)) in terms of \(n\). [2]
Given that \(n = 2\)
  1. find Var(3\(X\)). [3]