Probability

Question 1

Ratio rule?

Answer 1

P(A) = m/n

m = number of all outcomes when A is true 
n = number of all possible outcomes

Question 2

Addition rule?

Answer 2

P(A or B) = P(A) + P(B),
= P(A) + P(B) – P(A and B)
m = number of all outcomes when A is true
n = number of all possible outcomes

Question 3

Multiplication rule?

Answer 3

P(A and B) = P(AB)

               = P(A)×P(B) if A and B are independent events 
               = P(A)×P(B|A) if A and B are dependent events

Question 4

Conditional Probability rule?

Answer 4

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