Page 96 - Knowledge Organiser Yr9 24-25

Knowledge Base: Mathematics Topic 28: Combined Events Year 9 | Autumn Term, 2nd Half
By the end of this topic you should be able to:
• Calculate probability as a fraction, decimal or percent
• Recognise if events are independent or not
• Construct and use sample space diagrams
• Construct and use tree diagrams
• Recognise sets and display using venn diagrams
• Understand and use set notation to calculate probability
Language
Meaning
Example
Probability
A measure of how likely an event is to occur.
The probability of it raining tomorrow is 30%.
Mutually exclusive
Events that cannot both happen together.
Raining and not raining are mutually exclusive results.
Outcome
Possible result of a trial.
The possible outcomes of rolling a dice is 1, 2, 3, 4, 5, 6.
Event
A set of outcomes.
'Rolling an even number' on a dice is an event.
Experimental Probability
The number of favourable outcomes divided by the total number of outcomes in an experiment.
If a coin is tossed 50 times and comes up heads 23 times, then the experimental probability is 23
50
Theoretical Probability
Assuming all outcomes are equally likely, the number of favourable outcomes divided by the total number of outcomes.
For a regular dice, the theoretical probability of obtaining a factor of 6 (that is 1, 2, 3 or 6) is 46 = 23
Important things to remember:
1) Probability of an event is written as P(A)
2) P(A) = Number of outcomes belonging to event
Total number of equally likely outcomes 3) Probability of event not happening = 1- P(A)
Worked examples
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