Probability

Question 1

Probability of an event

Answer 1

P(A) = n(A)/n(Ω)

Question 2

Probability of A and B both happening when they’re independent

Answer 2

P(A ∩ B) = P(A) P(B)

Question 3

Probability of either A or B if they’re mutually exclusive

Answer 3

P(A U B) = P(A) + P(B)

Question 4

Probability of only A or only B if they are NOT mutually exclusive

Answer 4

P(A U B) = P(A) + P(B) - P(A ∩ B)