Conditional probability is the probability of an outcome occurring given that another event has occurred.

Mutually exclusive events have no outcomes in common.

Event A is independent of event B if the probability of event A occurring is not affected by whether or not event B occurs.

Conditional probability in a two-way table

Maths

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.

Conditional probability

The probability of an outcome occurring given that another event has occurred is called {{}} probability.

Taking a marble at random from a bag, replacing it and then taking another

Taking a marble at random from a bag, keeping it and then taking another

Select the example of events which are not independent.

The table shows the types of marble in a bag. Match each event to its probability.

 A marble is taken at random from a box of blue and green marbles. Alex works out that P(swirl and blue) = 0. This shows the event 'taking a blue marble' and the event 'taking a swirl marble' are...

A 20-sided die with integers from 1 to 20 written on it is rolled once. Select the pair of mutually exclusive events.

A deck of cards has a number on it (either prime or non-prime), and a symbol (a circle, square, or wave). A card is selected at random from the deck. Find P(square | prime).

Which symbol is used to represent the union of two sets?

What region is shown shaded in this Venn diagram? 

ξ = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}, A = {multiples of 4}, B = {factors of 12}. Find P(A' ∩ B').

Which combination of events is highlighted in the tree diagram?

Lucas and Izzy each play one game of chess that they can either win or lose.  P(Lucas wins ∩ Izzy wins) = {{ }} (give your answer as a decimal). 

This lesson will be removed by end of Summer Term 2025.

Conditional probability in a two-way table

Lesson outcome

This lesson will be removed by end of Summer Term 2025.