probability is a measure of how likely it is that an event will happen.

a tree diagram allows choices and outcomes for a sequence of events to be displayed.


Key Skills

  • use the correct words when talking about probabilities
  • calculate probabilities for events such as rolling dice and tossing coins
  • calculate probabilities for multiple events such as getting a head with a coin followed by a rolling a six on a die
  • find the expected value when carrying out several trials e.g. how many heads do you expect to get on 10 tosses of a coin
  • given a set of choices arrange them in a tree diagram
  • calculate outcomes from a tree diagram


median, tree diagram, stem and leaf diagramprobability,experimenttrialoutcome
sample spaceeventequally likely outcomesexpected value.