CAIE S2 2010 November — Question 2

Exam BoardCAIE
ModuleS2 (Statistics 2)
Year2010
SessionNovember
TopicPoisson Distribution
TypeTwo independent Poisson sums

2 People arrive randomly and independently at a supermarket checkout at an average rate of 2 people every 3 minutes.
  1. Find the probability that exactly 4 people arrive in a 5 -minute period. At another checkout in the same supermarket, people arrive randomly and independently at an average rate of 1 person each minute.
  2. Find the probability that a total of fewer than 3 people arrive at the two checkouts in a 3 -minute period.