Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Probability Notation Help

  1. Nov 5, 2012 #1
    In probability, P(A) is the probability of event A occurring.

    What is O(A), in the same context? I've tried looking this up, but I can't find the definition/explanation of this notation anywhere.

    For an example, see the definition of "Bayes' rule".
  2. jcsd
  3. Nov 5, 2012 #2


    User Avatar
    Science Advisor

    Do you mean the definition at Wikipedia? It defines O in the fourth equation under "Derivation".
  4. Nov 15, 2012 #3
    It's not really defining O there, is it? It's defining an equation that uses O, sure, but it still doesn't explain what the notation "O" represents. But maybe I just don't understand the equation.

    Regardless, the answer I was looking for is:

    O(A) is the "Odds" of event A occurring (versus event A not occurring), whereas P(A) is the "Probability" of event A occurring. (i.e., the number of outcomes where A occurs over the total number of outcomes.)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook