The probability of an event is a measure of the likelihood that the event will occur. By convention, statisticians have agreed on the following rules.
The probability of any event can range from 0 to 1. The probability of event A is the sum of the probabilities of all the sample points in event A. The probability of event A is denoted by P(A).Thus, if event A were very unlikely to occur, then P(A) would be close to 0. And if event A were very likely to occur, then P(A) would be close to 1.
