Free Union Probability Calculator
Calculate the probability that at least one of two events occurs using the addition rule.
P(A or B)
0.700000
P(A or B) as %70.0000
P(Neither)0.300000
P(A or B) vs P(A)
How to Calculate Union Probability
Formula
P(A or B) = P(A) + P(B) - P(A and B)
The addition rule accounts for the overlap between events A and B. If you simply add P(A) and P(B), the intersection is counted twice, so you subtract P(A and B) once. For mutually exclusive events, P(A and B) = 0.
Example Calculation
P(A) = 0.3, P(B) = 0.5, P(A and B) = 0.1. Find P(A or B).
- 01P(A or B) = P(A) + P(B) - P(A and B)
- 02P(A or B) = 0.3 + 0.5 - 0.1
- 03P(A or B) = 0.7
- 04P(Neither) = 1 - 0.7 = 0.3
Frequently Asked Questions
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