By tossing a coin once, what is the probability of having a head? Easy question. If a coin is fair, it is 50%. In other words, if you bet a head as outcome and it realized, you succeed. If not, you failed. Succeed or not succeed, occurrence or not occurrence, gain a sale or do not gain, all these outcomes can be translated as 0 and 1. The coin is one of the cases where you cannot control the probabilities. However, in the real world, the events do not occur randomly, without