Probability Calculator
P(¬A): Complement
0.6
P(A ∪ B)
0.58
P(A ∩ B)
0.12
P(A | B)
0.4
P(B | A)
0.3
FAQ
Probability theory
What is Bayes Theorem?
P(A|B) = P(B|A)·P(A) / P(B). Updates the probability of A given new evidence (B). Core of probabilistic reasoning, Bayesian statistics, and ML.
Independent events?
Two events A and B are independent if P(A ∩ B) = P(A)·P(B), i.e. one does not affect the other. Otherwise they are dependent and P(A ∩ B) must be provided.
What does the Bayes theorem say?
It says how to update the probability of a hypothesis when new information arrives: you multiply the starting probability by the probability of the observed data, and divide by the probability of that data.
When are two events independent?
When the probability that they both happen is the product of their probabilities, that is, when one happening does not change the other. When they are dependent, the joint probability goes in by hand.
What is the difference between union and intersection?
The union is the probability that at least one of the two events happens, the intersection that both do. In the union the probabilities are added and the intersection subtracted, so it is not counted twice.