## DEFINITION of 'Unconditional Probability'

The probability that an event will occur, not contingent on any prior or related results. An unconditional probability is the independent chance that a single outcome results from a sample of possible outcomes. To find the unconditional probability of an event, sum the outcomes of the event and divide by the total number of possible outcomes.

Also referred to as marginal probability.

## BREAKING DOWN 'Unconditional Probability'

Conditional probability measures the chance of an occurrence ignoring any knowledge gained from previous or external events. Since this probability ignores new information, it remains constant. For example, let's examine a group of stocks. A stock can either be a winner, which earns a positive income, or a loser, which has a negative income. Out of five stocks, stock A and B are winners, while C, D and E are losers. What is the unconditional probability of choosing a winning stock? Since two outcomes out of a possible five will produce a winner, the unconditional probability is 40% ( 2 / 5 ).