OCR S2 2010 June — Question 6

Exam BoardOCR
ModuleS2 (Statistics 2)
Year2010
SessionJune
TopicApproximating the Poisson to the Normal distribution
TypeMultiple approximations in one question

6
  1. The random variable \(D\) has the distribution \(\operatorname { Po } ( 24 )\). Use a suitable approximation to find \(P ( D > 30 )\).
  2. An experiment consists of 200 trials. For each trial, the probability that the result is a success is 0.98 , independent of all other trials. The total number of successes is denoted by \(E\).
    1. Explain why the distribution of \(E\) cannot be well approximated by a Poisson distribution.
    2. By considering the number of failures, use an appropriate Poisson approximation to find \(\mathrm { P } ( E \leqslant 194 )\).