Prior probability

Prior probability is like a guess about something before you know for sure. For example, if you want to know what the chances are of getting a certain color of jellybean from a jar without looking, you can use something called prior probability.

Prior probability means looking at all the jellybeans in the jar and guessing how many of each color there might be. You can even use the colors of the jellybeans you can see to make a guess, like if you can see mostly red jellybeans then you might think there are more red jellybeans in the jar than any other color. This guess is the prior probability.

If you pick out a jellybean without looking, you now know for sure what color it is, so the prior probability (your guess) might be right or wrong.