It is the feature that assumes a bet, or a lottery, in case that are known the probabilities of a random distribution of the event object of the game and in case of positive outcome, the sum received in premium is equal to the bet multiplied by the reciprocal of chances of winning. In particular, given the likelihood of the occurrence of random event (Px), the price you pay to play the game (B), is equal to the product of the award sum (s) for the probability of winning (Pv).
On the contrary, it is not fair game when there is a fee or profit (?) of the operator of the game.
AA.VV., Matematica Finanziaria, Monduzzi Editore, 1998
Grinstead M. C., Snell J. L., Introduction to Probability, American Mathematical Society, 1997
Editor: Giuliano DI TOMMASO