OCR MEI S2 2009 June — Question 2

Exam BoardOCR MEI
ModuleS2 (Statistics 2)
Year2009
SessionJune
TopicPoisson Distribution
TypeState conditions only

2 Jess is watching a shower of meteors (shooting stars). During the shower, she sees meteors at an average rate of 1.3 per minute.
  1. State conditions required for a Poisson distribution to be a suitable model for the number of meteors which Jess sees during a randomly selected minute. You may assume that these conditions are satisfied.
  2. Find the probability that, during one minute, Jess sees
    (A) exactly one meteor,
    (B) at least 4 meteors.
  3. Find the probability that, in a period of 10 minutes, Jess sees exactly 10 meteors.
  4. Use a suitable approximating distribution to find the probability that Jess sees a total of at least 100 meteors during a period of one hour.
  5. Jess watches the shower for \(t\) minutes. She wishes to be at least \(99 \%\) certain that she will see one or more meteors. Find the smallest possible integer value of \(t\).