Conditional Probability

_Part Four

The probability of event B happening, given that event A already happened, is called the conditional probability. The conditional probability of B, given A is written as P(B | A), and is read as "the probability of B given A".

P(B|A) means the probability of B given A.

General Multiplication Rule For any two events A and B
P(A ∩ B) = P(A)P(B|A)
P(A and B) = P(A)P(B|A)
  • If A and B are independent, P(B|A) = P(B)