# Probability concepts

## What does P(A) represent?

The probability of A occuring

## What does P(A ∩ B) represent?

The probability of both a and b occuring

## what does P(A U B) represent?

The probability of a or b on their own or a and b together occuring

## What does P(A') represent?

The probability of not a occuring

## What does P(A U B) = P(A' ∩ B') represent?

The probability of neither a or b occuring

## When are probability trees used?

When there is a sequence of events

## What does mutally exclusive mean?

Events that cannot both occur at the same time

## What does not mutally exclusive mean?

Events that can both occur at the same time

## When do complementary events occur?

When there are only two outcomes

## What is conditional probability?

When the probability of an event is altered by the occurence of another event

## What is an independent event?

The occurence of one event makes no difference to the probability of the second event