Tree diagrams & Bayes theorem

• Why are tree diagrams useful?


  To find dependent probabilities.
• When should tree diagrams be used?


  • when events are independent
  • probabilities are quoted in given form
• Exam technique for tree diagrams


  • always multiply along branches
  • look out for questions where selection is happening
• Why is Bayes theorem useful?


  It gives us the probability for events based on a previous event occurring.
• Key tip for Bayes theorem


  Draw a tree diagram, it then becomes a standard given rule question.
• Exam technique for Bayes theorem


  • tree should be drawn
  • don't use formula in booklet
  • may not be stated - have to spot that a previous event has occured