According to​ Bayes' Theorem, the probability of event​ A, given that event B has​ occurred, is as follows.
Upper P left parenthesis Upper A vertical line Upper B right parenthesis equals StartFraction Upper P left parenthesis Upper A right parenthesis times Upper P left parenthesis Upper B vertical line Upper A right parenthesis Over Upper P left parenthesis Upper A right parenthesis times Upper P left parenthesis Upper B vertical line Upper A right parenthesis plus Upper P left parenthesis Upper A prime right parenthesis times Upper P left parenthesis Upper B vertical line Upper A prime right parenthesis EndFraction
Use​ Bayes' Theorem to find Upper P left parenthesis Upper A vertical line Upper B right parenthesis using the probabilities shown below.
Upper P left parenthesis Upper A right parenthesis equals one fourth
​, Upper P left parenthesis Upper A prime right parenthesis equals three fourths
​, Upper P left parenthesis Upper B vertical line Upper A right parenthesis equals one tenth
​, and Upper P left parenthesis Upper B vertical line Upper A prime right parenthesis equals one half