Edexcel FS1 2020 June — Question 2

Exam BoardEdexcel
ModuleFS1 (Further Statistics 1)
Year2020
SessionJune
TopicApproximating the Binomial to the Poisson distribution
TypeJustify Poisson approximation only

  1. The discrete random variables \(W , X\) and \(Y\) are distributed as follows
$$W \sim \mathrm {~B} ( 10,0.4 ) \quad X \sim \operatorname { Po } ( 4 ) \quad Y \sim \operatorname { Po } ( 3 )$$
  1. Explain whether or not \(\mathrm { Po } ( 4 )\) would be a good approximation to \(\mathrm { B } ( 10,0.4 )\)
  2. State the assumption required for \(X + Y\) to be distributed as \(\operatorname { Po } ( 7 )\) Given the assumption in part (b) holds,
  3. find \(\mathrm { P } ( X + Y < \operatorname { Var } ( W ) )\)