What do you mean by further tree diagrams?

• The tree diagrams used here are no more complicated than those in the first?Tree Diagrams?revision note, however
  • The wording/terminology used in questions and on diagrams may now involve the use of?set?notation including the symbols ∪(union), ∩(intersection) and ‘ (complement)
    • e.g.? P(A') would be used for “P(not?A)”
  • Conditional probability?questions can be solved using tree diagrams

How do I solve conditional probability problems using tree diagrams?

• Interpreting questions in terms of?AND (∩),?OR (∪),?complement?( ‘ ) and?“given that”?( | )
• Condition probability?may now be involved too
• This makes it harder to know where to start and how to complete the probabilities on a tree diagram
  • e.g. If given, possibly in words, ?then?event?A?has already occurred so start by looking for the branch?event?A?in the?1st?experiment,?and?then ?would be the?branch?for?event??in the?2nd?experiment

Similarly, ?would require starting with?event “?”?in the?1st?experiment?and?event?B?in the?2nd?experiment

• The diagram above gives rise to some probability formulae you will see in Probability Formulae
• (“given?that”) is the probability on the branch of the 2nd?experiment
• However, the “given?that” statement ?is more complicated and a matter of working backwards
  • from Conditional Probability,
  • from the diagram above,
  • leading to?
  • This is quite a complicated looking formula to try to remember so use the logical steps instead – and a clearly labelled tree diagram!

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