The probability that an event will occur is the proportion of times the event is expected to happen in a suitably large experiment.

A set of events are exhaustive if at least one of them has to occur whenever the experiment is carried out.

Mutually exclusive events have no outcomes in common.

Venn diagrams are a representation used to model statistical/probability questions. Commonly circles are used to represent events.

Problem solving with conditional probability

Maths

Checking and securing displaying outcomes

Checking and securing exhaustive events

Probabilities involving algebra

Frequency trees

Checking and securing calculating probabilities from tables

Checking and securing calculating probabilities from diagrams

Experimental probability

Experimental vs theoretical probability

Set notation

Conditional probability in a two-way table

Conditional probability in a Venn diagram

Conditional probability in a tree diagram

In this unit, pupils use their knowledge of calculating theoretical probabilities and extend this understanding to calculating conditional probabilities using all of the representations encountered in the prior unit.

In this unit, pupils use their knowledge of calculating theoretical probabilities and extend it to calculate conditional probabilities.

Conditional probability

Starting with the least likely, put these probabilities in order of likelihood.

The probability of three outcomes to a trial are shown in the table. 
The outcomes are exhaustive and mutually exclusive. Find P(C).

Jacob and Sofia each play a tennis match. Find the probability that both Jacob and Sofia win their match.

Jacob and Sofia each play a tennis match. Find the probability that at least one of them wins their match.

A box contains green and blue marbles. Some of the marbles have swirls on them. The Venn diagram shows the number of each type. P(B) = {{ }}. Give your answer as a decimal.

A box contains green and blue marbles. Some of the marbles have swirls on them. The Venn diagram shows the number of each type. P(S ∪ B) = {{ }}. Give your answer as a decimal.

Mutually __________ events have no outcomes in common.

Sofia has to catch a bus and then a train to get to school. When the bus is late, Sofia is more likely to miss the train and so be late for school. Match each value to its probability.

Sofia has to catch a bus and then a train to get to school. When the bus is late, Sofia is more likely to miss the train and so be late for school.  P(Sofia is late for school) = {{ }}.

Here is a general probability tree. Which of these probabilities give the probability of the highlighted events?

One marble is taken at random from a bag of 7 purple and 5 green marbles. The marble is not replaced. A second marble is then taken. The tree diagram shows these two events. Find the value of $$z$$.

One marble is taken at random from a bag of purple and green marbles. The marble is not replaced. A second marble is then taken. The tree diagram shows the two events. Find P(both marbles are purple).

Starter Quiz

Mutually __________ events have no outcomes in common.