Y2 chapter 2 Probability

Question 1

What does B | A mean?

Answer 1

the probability of B given that A has already happened.

Question 2

How to draw a two way table?

Answer 2

event and event complement.

Question 3

What is a formula for P(AuB) and why does this formula work?

Answer 3

P(A U B) = P(A) + P(B) - P(A ∩ B).

It works as the final subtraction prevents the intersection being counted twice.

Question 4

What is the formula for P(B|A)

Answer 4

P(B|A) = P(AnB) / P(A)

Question 5

What is the formula for P(AnB)?

Answer 5

P(AnB) = P(A) x P(B|A)