Edexcel S2 2018 October — Question 7

Exam BoardEdexcel
ModuleS2 (Statistics 2)
Year2018
SessionOctober
TopicPoisson Distribution
TypeFinding minimum n for P(X=0) threshold

7. Members of a conservation group record the number of sightings of a rare animal. The number of sightings follows a Poisson distribution with a rate of 1 every 2 months.
  1. Find the smallest value of \(n\) such that the probability that there are at least \(n\) sightings in 2 months is less than 0.05
  2. Find the smallest number of months, \(m\), such that the probability of no sightings in \(m\) months is less than 0.05
  3. Find the probability that there is at least 1 sighting per month in each of 3 consecutive months.
  4. Find the probability that the number of sightings in an 8 month period is equal to the expected number of sightings for that period.
  5. Given that there were 4 sightings in a 4 month period, find the probability that there were more sightings in the last 2 months than in the first 2 months.