Probability

You will be able to

• Calculate relative frequency as frequency ÷ number of trials and use it as an estimate of a probability.
• Explain why more trials give a more reliable estimate, and use relative frequency to decide whether a dice or spinner is biased.
• Calculate an expected frequency as the number of trials × the probability.

You will be able to

• List all the outcomes of two combined experiments in a sample-space diagram.
• Calculate the probability of an event as the number of favourable outcomes ÷ the total number of equally likely outcomes, in its simplest form.
• Compare the probability from a sample space with the relative frequency from repeated trials.

You will be able to

• Draw a tree diagram for two or three events and label every branch with its probability.
• Calculate combined probabilities by multiplying along the branches and adding the probabilities of different paths.
• Explain how the branch probabilities change when counters are taken without replacement.

You will be able to

• Calculate a conditional probability from a two-way table, a Venn diagram or a tree diagram by restricting to the given group.
• Explain why P(A given B) is usually different from P(B given A).
• Determine whether two events are independent by checking whether P(A given B) = P(A).