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Probability Calculator
Calculate the probability of single and multiple independent events occurring.
Enter Probabilities
Probability Calculations
P(A does NOT occur):50.00% (0.5000)
P(B does NOT occur):70.00% (0.7000)
P(Both A AND B occur):15.00% (0.1500)
P(At least one occurs - A OR B):65.00% (0.6500)
P(Event A occurs but NOT B):35.00% (0.3500)
P(Neither Event occurs):35.00% (0.3500)
Understanding Probability Rules
Probability describes the likelihood of an event occurring, scaled on a range from 0 (impossible) to 1 (absolute certainty). When dealing with multiple events, we use standard probability rules:
- Independent Events: Event A and Event B are independent if the outcome of one does not affect the other (like rolling two separate dice).
- The AND Rule (Multiplication): The probability of both independent events A and B occurring together is calculated by multiplying their probabilities:
P(A AND B) = P(A) × P(B). - The OR Rule (Addition): The probability of at least one event A or B occurring is calculated by adding their probabilities and subtracting the overlap (to avoid double-counting):
P(A OR B) = P(A) + P(B) − P(A AND B).