Probability Trees Flashcards

GCSE Mathematics (Edexcel) 1MA1

Probability tree diagram

A diagram used to represent all possible outcomes of a sequence of events and their probabilities.

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Probability tree diagram

A diagram used to represent all possible outcomes of a sequence of events and their probabilities.

Branches in a probability tree

Each branch represents a possible outcome of an event, labelled with its probability.

Sum of probabilities on branches

The probabilities on branches from the same point must add up to 1.

Multiplying along branches

To find the probability of a sequence of events, multiply the probabilities along the branches.

Adding probabilities in a tree

To find the probability of multiple outcomes, add the probabilities of the relevant branches.

Independent events in a tree

Events are independent if the outcome of one event does not affect the probability of the other.

Dependent events in a tree

Events are dependent if the outcome of one event affects the probability of the other.

Labelling probabilities in a tree

Probabilities should be written as fractions, decimals, or percentages on the branches.

Total probability of all outcomes

The total probability of all possible outcomes in a probability tree is always 1.

Using a tree for 'at least one' problems

To solve 'at least one' problems, calculate the probability of the complementary event and subtract from 1.

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