C5 - Probability

• An experiment is a repeatable process that gives rise to a number of outcomes.
• An event is a collection of one or more outcomes.
• A sample space is the set of all possible outcomes.
• Where outcomes are equally likely the probability of an event is the number of outcomes in the event divided by the total number of possible outcomes.
• All events have probability between 0 (impossible) and 1 (certain). Probabilities are usually written as fractions or decimals.
• A venn diagram can be used to represent events graphically. Frequencies or probabilities can be placed in the regions of the venn diagram.
• When events have no outcomes in common they are called mutually exclusive.
• For mutually exclusive events, P(A or B) = P(A) + P (B)
• When one event has no effect on another, they are independent.
• For independent events, P(A and B) = P(A) x P(B)
• A tree diagram can be used to show the outcomes of two (or more) events happening in succession.