WJEC Unit 4 Specimen — Question 2

Exam BoardWJEC
ModuleUnit 4 (Unit 4)
SessionSpecimen
TopicGeometric Distribution
TypeGame theory with alternating players

2. Mary and Jeff are archers and one morning they play the following game. They shoot an arrow at a target alternately, starting with Mary. The winner is the first to hit the target. You may assume that, with each shot, Mary has a probability 0.25 of hitting the target and Jeff has a probability \(p\) of hitting the target. Successive shots are independent.
  1. Determine the probability that Jeff wins the game
    i) with his first shot,
    ii) with his second shot.
  2. Show that the probability that Jeff wins the game is $$\frac { 3 p } { 1 + 3 p }$$
  3. Find the range of values of \(p\) for which Mary is more likely to win the game than Jeff.