Probability Calculator
Enter the probabilities of two events A and B and their joint probability P(A ∩ B). The calculator returns the complements, the union, both conditional probabilities and tells you whether the events are independent.
Frequently asked questions
How is P(A ∪ B) computed?
By the inclusion-exclusion principle: P(A ∪ B) = P(A) + P(B) − P(A ∩ B).
What does the independence check do?
It compares P(A)·P(B) against the given P(A ∩ B). Equality means the events are independent; a mismatch means dependence.
How is conditional probability defined?
P(A | B) = P(A ∩ B) / P(B) — the probability of A given that B has already occurred.