Thus , all the possible outcomes of a random experiment form a set of exhaustive events. Hence the set of exhaustive events forms a sure event. As an example , the two events head and tail in the tossing of an unbiased coin once are exhaustive events because no event other than a head or a tail can occur in this random experiment. Similarly when a die is cast , the six events 1,2,3,4,5 and 6 are exhaustive .