Examples of what pupils should know and be able to do
Pupils need to know that, for two mutually exclusive events, the probability of either occurring is the sum of the two probabilities.
Probing questions
If I throw a coin and roll a dice the probability of either 5 or a head is 7/12. This is not 1/2 + 1/6. Why not?
What if pupils find this a barrier?
Return to a simpler case (step 7), e.g. the roll of a dice. Ask for the probability of a number less than 6. Ask pupils to explain their answer. Ask for the probabilities of each of the numbers 1, 2, 3, 4 and 5. Hence show the equivalence between their answer and the sum of the individual probabilities.
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