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

The probability scale

Maths

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

In the prior unit, pupils learnt techniques for systematically listing all of the possible outcomes for both one event and two events. In this unit, pupils use lists of outcomes to find theoretical probabilities. 

Probability: theoretical probabilities

The letter E on the scale represents a probability of {{}}%.

Which probabilities are equivalent to an 'even chance'?

What is the probability of an event that is impossible?

Which is the probability that this spinner lands on 'win'?

A trial has three possible outcomes: {A, B, C}. P(A) = $${1}\over{2}$$. P(B) = $${1}\over{3}$$. P(C) = $${1}\over{6}$$. Which outcome is most likely to happen?

The probability on an outcome is 20%. Approximately how many times could you expect the outcome to occur in 500 trials?

Which letter on the scale of likelihoods represents 'even chance'?

What does the letter A represent on the scale of likelihoods?

Which word describes the likelihood of an outcome that is guaranteed to happen?

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

The probability scale

Lesson outcome

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