Bayes Theorem

Not Reviewed
Equation / Last modified by MichaelBartmess on 2018/05/26 02:17
`P(A|B) = `
vCollections.Bayes Theorem

Bayes' Theorem, `P(A|B) = (P(B|A)*P(A))/(P(B))`, computes the probability of event A occurring if event B is true.


  • P(A) is the probability of A being true independent of B
  • P(B) is the probability of B being true independent of A
  • P(B|A) is the probability of B being true if A has been observed (is true)


Probabilities are expressed here as decimals between 0 and 1, where 0 means there is no chance of an occurrence and 1 implies a certainty of occurrence.  For example, an event with a 20% chance of occurrence has a probability of 0.2.  


Baye's Theorem is helpful when considering test results, especially medical test results.  For example, you may have tested positive for a disease like Zika or HIV.  But there is a potential for a FALSE positive.  CLICK HERE for an insightful blog on how a false positive can be judged.


This equation, Bayes Theorem, is listed in 1 Collection.