OCR S3 2012 June — Question 5

Exam BoardOCR
ModuleS3 (Statistics 3)
Year2012
SessionJune
TopicLinear combinations of normal random variables
TypePure expectation and variance calculation

5 The discrete random variables \(X\) and \(Y\) are independent with \(X \sim \mathrm {~B} \left( 32 , \frac { 1 } { 2 } \right)\) and \(Y \sim \operatorname { Po } ( 28 )\).
  1. Find the values of \(\mathrm { E } ( Y - X )\) and \(\operatorname { Var } ( Y - X )\).
  2. State, with justification, an approximate distribution for \(Y - X\).
  3. Hence find \(\mathrm { P } ( | Y - X | \geqslant 3 )\).