Welcome to the first installment of a Narwhal's Guide to Bayes' Rule. If you don't know what a narwhal is, wikipedia can help you. Images can be clicked to be made larger.

An simple example of its use with respect to mermaids and singing marine mammals.

Another example of Bayes' Rule, as applied to single horned land mammals and unicorns: an unexpected result.

Another way to think of what the equation means.

In the next installment(s), there will be a treasure chest with a curse (you can't see what you are picking up but you can feel the spherical pearls, gold doubloons, and worthless iron coins, how will you choose?), another cursed treasure chest (now with worthless marbles and coin shaped pearls), then using Bayes' to look at evaluating risks (airplanes), forecasting, and machine learning, and finally how to remember the darn thing, additional resources and problems. You can see it all in the finished PDF!

In the meantime, if you want to know more, take a look at my favorite Bayes visualization method and great warehouse of explanation techniques.