Statistics & probability
Bayes probability calculator
Update an event probability using evidence rates you supply.
A clear answer. Here’s how.
P(A|E)=P(E|A)P(A)/[P(E|A)P(A)+P(E|not A)(1−P(A))]. Reports the evidence probability and posterior. Your prior and likelihoods must refer to the same event definitions. Evidence with zero model probability is rejected; the inputs are not estimated or validated against real observations.
See a worked example
Worked example
A fixed demonstration, separate from the values you enter above.
- Prior P(A)
- 0.1
- P(evidence | A)
- 0.8
- P(evidence | not A)
- 0.2
Example result
- Posterior P(A | evidence)
- 0.307692307692
- Evidence probability
- 0.26
- Prior P(A)
- 0.1