OCR S3 2007 June — Question 7

Exam BoardOCR
ModuleS3 (Statistics 3)
Year2007
SessionJune
TopicCumulative distribution functions
TypeCDF of transformed variable

7 The continuous random variable \(X\) has (cumulative) distribution function given by $$\mathrm { F } ( x ) = \begin{cases} 0 & x < 1
1 - \frac { 1 } { x ^ { 4 } } & x \geqslant 1 \end{cases}$$
  1. Find the (cumulative) distribution function, \(\mathrm { G } ( y )\), of the random variable \(Y\), where \(Y = \frac { 1 } { X ^ { 2 } }\).
  2. Hence show that the probability density function of \(Y\) is given by $$g ( y ) = \begin{cases} 2 y & 0 < y \leqslant 1
    0 & \text { otherwise } \end{cases}$$
  3. Find \(\mathrm { E } ( \sqrt [ 3 ] { Y } )\).