CAIE S1 2010 November — Question 3

Exam BoardCAIE
ModuleS1 (Statistics 1)
Year2010
SessionNovember
TopicTree Diagrams
TypeConditional probability from tree

3 It was found that \(68 \%\) of the passengers on a train used a cell phone during their train journey. Of those using a cell phone, \(70 \%\) were under 30 years old, \(25 \%\) were between 30 and 65 years old and the rest were over 65 years old. Of those not using a cell phone, \(26 \%\) were under 30 years old and \(64 \%\) were over 65 years old.
  1. Draw a tree diagram to represent this information, giving all probabilities as decimals.
  2. Given that one of the passengers is 45 years old, find the probability of this passenger using a cell phone during the journey.