Investopedia explains Prior Probability Prior
probabilities represent what we originally believed before new evidence
is uncovered. New information is used to produce updated probabilities
and is a more accurate measure of a potential outcome. For example,
three acres of land have the labels A, B and C. One acre has reserves
of oil below its surface, while the other two do not. The probability
of oil being on acre C is one third, or 0.333. A drilling test is
conducted on acre B, and the results indicate that no oil is present at
the location. Since acres A and C are the only candidates for oil
reserves, the prior probability of 0.333 becomes 0.5, as each acre has
one out of two chances. |