Probability for Beginners: Basic Rules, Formulas & Examples

Probability is the mathematical measure of the likelihood that a specific event will occur. It ranges from 0 (impossible event) to 1 (certain event).

P(Event) = (Number of Favorable Outcomes) ÷ (Total Number of Possible Outcomes)

• Complement Rule: P(Not A) = 1 − P(A)
• Addition Rule (Mutually Exclusive): P(A or B) = P(A) + P(B)
• Multiplication Rule (Independent Events): P(A and B) = P(A) × P(B)