AQA S2 2016 June — Question 1 7 marks

Exam BoardAQA
ModuleS2 (Statistics 2)
Year2016
SessionJune
Marks7
TopicPoisson Distribution
TypeSum of independent Poisson processes

1 The water in a pond contains three different species of a spherical green algae:
Volvox globator, at an average rate of 4.5 spheres per \(1 \mathrm {~cm} ^ { 3 }\);
Volvox aureus, at an average rate of 2.3 spheres per \(1 \mathrm {~cm} ^ { 3 }\);
Volvox tertius, at an average rate of 1.2 spheres per \(1 \mathrm {~cm} ^ { 3 }\).
Individual Volvox spheres may be considered to occur randomly and independently of all other Volvox spheres. Random samples of water are collected from this pond.
Find the probability that:
  1. a \(1 \mathrm {~cm} ^ { 3 }\) sample contains no more than 5 Volvox globator spheres;
  2. a \(1 \mathrm {~cm} ^ { 3 }\) sample contains at least 2 Volvox aureus spheres;
  3. a \(5 \mathrm {~cm} ^ { 3 }\) sample contains more than 8 but fewer than 12 Volvox tertius spheres;
  4. a \(0.1 \mathrm {~cm} ^ { 3 }\) sample contains a total of exactly 2 Volvox spheres;
  5. a \(1 \mathrm {~cm} ^ { 3 }\) sample contains at least 1 sphere of each of the three different species of algae.
    [0pt] [3 marks]