How to Use the Independent Events Probability Calculator
Two events are independent when whether one happens has no effect on the probability of the other. For example, flipping a coin twice — the first flip doesn't affect the odds of the second, so the two flips are independent. This calculator takes the probabilities of two independent events A and B and calculates the AND probability (both happen), the OR probability (at least one happens), and the NOT probability (an event doesn't happen) all at once.
For independent events, the AND probability is simply the two probabilities multiplied together (P(A)×P(B)). The OR probability adds the two probabilities and then subtracts the AND probability once, since it would otherwise be counted twice (P(A)+P(B)-P(A∩B)). The NOT probability is just 100% minus that event's probability.
Probabilities must be entered between 0% and 100%, and these formulas are only exact when the two events genuinely don't affect each other.
Frequently Asked Questions
Not accurately. If one event affects the other (dependent events), you'd need conditional probability instead, and this calculator's multiplication formula (AND=P(A)×P(B)) would give an incorrect result.
Because the case where both events happen (AND) would get counted twice. You have to subtract P(A∩B) once from P(A)+P(B) to get the correct OR probability.