Basic Probability Notation: Independence of Variables

• If events A and B are independent,
  P(A and B) = P(A) P(B).

• If events A and B are independent,
  P(A or B) = 1 - (1 - P(A))(1 - P(B)) = P(A) + P(B) - P(A)P(B).

These formulas permit us to use statistical information to determine possible causal connections between events.