StatsApps

Bayes' Theorem

Bayes' theorem gives the probability of an event, based on prior knowlede of related conditions. It is given as:

P(A|B) = [P(B|A)*P(A)] / P(B),

where A and B are two events, and P(B) cannot be equal to 0.

Resources

  1. GeoGebra applet on Bayes' theorem:

    Exploring Bayes' Theorem

    Users can use the applet to apply Bayes' theorem to find the probability that a person is actually infected given that the person has tested positive for a disease. The link provides a detailed description of how the applet can be used.

    Author: David Radcliffe from GeoGebra.
    License: GeoGebra License.

  2. Bayes' theorem calculator:

    Bayes' Theorem Calculator

    This web calculator allows users to enter three of:
    • The probability of event A;
    • The probability of event B;
    • The conditional probability of event B occurring given that A has happened; and
    • The conditional probability of event A occurring given that B has happened.
    The calculator displays the remaining probability.

    Author: Marcin Manias.
    Reviewed by Dominik Czernia, PhD candidate, and Jack Bowate.