In our everyday life, we often come across remarks like, “It will probably rain tonight” or “It is unlikely that India will beat Australia in the ODI series”. What do these statements imply? In both the cases, the statement doesn’t state anything conclusively, but tries to hint at the possible chances of occurrence or non-occurrence of an event, which is called Probability that an Event will occur or not occur, respectively.So basically Probability is the computation of the likelihood of an even.
For any Random Experiment, let the Sample Space (S) contains ‘b’ possible outcomes, while the set of Favorable Outcomes (A) contains ‘a’ possible outcomes, then the Probability of Event (A) is given by P(A) such that, P(A) = Number of Favorable Outcomes/ All possible Outcomes = n(A) / n(S) = a/b where 0 ≤ P(A) ≤ 1 always. The complement of A(probability of non-occurrence of Event A), is denoted as P(A’) = 1 – P(A). Set A’ contains all the Unfavorable cases.