Edexcel S2 2018 June — Question 5

Exam BoardEdexcel
ModuleS2 (Statistics 2)
Year2018
SessionJune
TopicApproximating the Poisson to the Normal distribution
TypeFind parameter from given probability

5. Cars stop at a service station randomly at a rate of 3 every 5 minutes.
  1. Calculate the probability that in a randomly selected 10 minute period,
    1. exactly 7 cars will stop at the service station,
    2. more than 7 cars will stop at the service station. Using a normal approximation, the probability that more than 40 cars will stop at the service station during a randomly selected \(n\) minute period is 0.2266 correct to 4 significant figures.
  2. Find the value of \(n\).