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      Lesson details

      Learning outcome

      I can assign a numerical value to an outcome to give the probability that the outcome will occur.

      Key learning points

      1. Probability is a measure of the likelihood of an outcome happening.
      2. An outcome can be assigned a numerical value from 0 to 1
      3. The probability scales shows the numerical values that an outcome might have.

      Keywords

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

      Common misconception

      Pupils think that 'likely' from the scale of likelihoods is only equal to a specific probability (e.g. 75%).

      All probabilities that are greater than 50% but less than 100% are equivalent to 'likely' on the scale of likelihoods.

      Teacher tip

      Question 4 in Task B contains a link to a Desmos file. If pupils have access to a web browser, they could use to link to simulate an experiment. If pupils do not have access to a web browser then the teacher could display the simulation on the screen or run it in advance and print off the results.

      Licence

      This content is © Oak National Academy Limited (2025), licensed on Open Government Licence version 3.0
      except where otherwise stated. See Oak's terms & conditions
      (Collection 2).

      Lesson video

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      Prior knowledge starter quiz

      6 Questions

      Q1.
      Which letter on the scale of likelihoods represents 'even chance'?

      An image in a quiz
      A
      B
      Correct answer: C
      D
      E

      Q2.
      What does the letter A represent on the scale of likelihoods?

      An image in a quiz
      certain
      even chance
      Correct answer: impossible
      likely
      unlikely

      Q3.
      Which word describes the likelihood of an outcome that is guaranteed to happen?

      Correct answer: certain
      even chance
      impossible
      likely
      unlikely

      Q4.
      Which percentage is equivalent to 0.1?

      0.001%
      0.01%
      0.1%
      1%
      Correct answer: 10%

      Q5.
      Which fraction is equivalent to 50%?

      Correct answer: $${1}\over{2}$$
      $${1}\over{5}$$
      $${1}\over{20}$$
      $${1}\over{50}$$

      Q6.
      What is 25% of 2000?

      Correct Answer: 500, five hundred

      6 Questions

      Q1.
      The letter E on the scale represents a probability of %.

      An image in a quiz
      Correct Answer: 100

      Q2.
      Which probabilities are equivalent to an 'even chance'?

      0.2
      Correct answer: $${1}\over{2}$$
      Correct answer: 0.5
      Correct answer: 50%
      $${1}\over{5}$$

      Q3.
      What is the probability of an event that is impossible?

      Correct Answer: 0, 0%, zero, 0 percent, zero percent

      Q4.
      Which is the probability that this spinner lands on 'win'?

      An image in a quiz
      1%
      Correct answer: 47%
      50%
      53%
      99%

      Q5.
      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?

      Correct answer: A
      B
      C

      Q6.
      The probability on an outcome is 20%. Approximately how many times could you expect the outcome to occur in 500 trials?

      20
      50
      Correct answer: 100
      200
      250

      To help you plan your 9 maths lesson on: The probability scale, download all teaching resources for free and adapt to suit your pupils' needs...