in the doctrine of chances, is applied to any contingent event, and is capable of being reduced to the rules of computation. Thus a sum of money in expectation when a particular event happens, has a determinate value before that event arrives; so that if a person is to receive any sum, say L10, when an event takes place which has an equal probability of happening and failing, the value of the expectation is half that sum, or L5; and in all cases the expectation of obtaining any sum is estimated by multiplying the value of the sum expected by the fraction which represents the probability of obtaining it. The expectation of a person who has three chances in five of obtaining L100, is equal to $\frac{3}{5} \times 100$, or L60, and the probability of obtaining L100 in this case is equal to $\frac{3}{5} = \frac{3}{5}$.

See PROBABILITIES.