Conditional Probability
Maths: Edexcel IGCSE Higher, topic 6.3.8
Conditional Probability
The conditional probability of event A given event B is the probability that event A happens given that event B happens. The event A given B can be written as A|B.
Conditional probability
- This is the general equation for conditional probability.
Independent events
- If events A and B are independent then P(A|B) = P(A).
Dependent events
- For dependent events the probability for both A and B occurring is:
- P(A and B) = P(A) × P(B|A)
- or P(A and B) = P(B) × P(A|B).
Test yourself on Conditional Probability
A bag contains 6 tiles, each with one of the letters in the word SENECA on them. If we pick two tiles at random from the bag and they are not replaced, what is the probability that we pick two Es?
A bag contains 6 tiles, each with one of the letters in the word SENECA on them. If we pick two tiles at random from the bag and they are not replaced, what is the probability that we pick two vowels?
A bag contains 6 tiles, each with one of the letters in the word SENECA on them. If we pick two tiles at random from the bag and they are not replaced, what is the probability that we pick two As?
A bag contains 6 tiles, each with one of the letters in the word SENECA on them. If we pick one tile from the bag, keep it, and then pick another tile, what is the probability that two Es were chosen?
A bag contains 6 tiles, each with one of the letters in the word SENECA on them. Given that we have picked the S in our first go, and do not replace it, what is the probability of picking an E with our second go?