Practice Flashcards
Flip to reveal answersState the conditional probability formula.
Track your progress — Sign up free to save your progress and get smart review reminders based on spaced repetition.
All 9 Flashcards — Conditional probability
Sign up free to track progress and get spaced-repetition review schedules.
Question
State the conditional probability formula.
Answer
P(A | B) = P(A ∩ B) ÷ P(B).
Question
What does P(A | B) mean?
Answer
The probability of A given that B has already occurred.
Question
Which event do you divide by?
Answer
The given event — the one after the '|'.
Question
If you only have P(A), P(B) and P(A ∪ B), how do you start?
Answer
Find P(A ∩ B) from the addition rule first.
Question
From a two-way table, what is the denominator for P(A | B)?
Answer
The total of the given group B (e.g. all students), not the whole sample.
Question
On a tree diagram, what kind of probability is a second-stage branch?
Answer
A conditional probability (given the first-stage outcome).
Question
How do you reverse a condition on a tree (e.g. P(cause | effect))?
Answer
Use P(cause ∩ effect) ÷ P(effect), with P(effect) the total over all paths.
Question
How is conditional probability linked to independence?
Answer
If P(A | B) = P(A), then A and B are independent.
Question
Rearrange to find P(A ∩ B) from P(A | B) and P(B).
Answer
P(A ∩ B) = P(A | B) × P(B).
Read the notes
Full study notes for Conditional probability
Topic 4.11 hub
Conditional probability
More from Topic 4.11
All flashcards in this topic
Math AA SL exam skills
Paper structures & tips
Track your progress with spaced repetition
Sign up free — Aimnova tells you exactly which cards to review and when, so you remember everything before your IB exam.
Start Free