Independent Events
Maths: Edexcel IGCSE Higher, topic 6.3.7
Independent and Dependent Events
Independent
- Two events are independent if they don't affect each other.
- For example if we toss a coin twice, the first event is independent of the second event. The results do not affect each other.
Dependent
- Two events are dependent if they do affect each other.
- For example ‘It is raining’ and ‘I take my umbrella to school’ are dependent events.
Picking balls from a bag
- Picking balls from a bag with replacement results in each pick being independent from the others.
- Balls not being replaced means the picks are dependent on each other. If we pick the only blue ball in our first pick we cannot pick it again.
Calculating Probabilities
For any two events
For independent events
For mutually exclusive events
- Mutually exclusive events can't both happen at the same time.
Test yourself on Independent Events
The probability of Maria getting a question right in her Spanish test is . What is the probability of her getting the first 2 questions correct?
The probability of Stella getting a question right in her Spanish test is . What is the probability of her getting the first 2 questions correct?
The probability of Georgia getting a question right in her Spanish test is . What is the probability of her getting the first 2 questions correct?
There are 3 balls in a bag. 1 is red and 2 are blue. What is the probability of drawing a blue ball and then a red ball. The first ball is NOT replaced after it has been drawn.
There are 3 balls in a bag. 1 is red and 2 are blue. What is the probability of drawing a red ball and then a blue ball. The first ball is NOT replaced after it has been drawn.