A Practical Overview on Comparison Discrete and Continuous Probability Distributions

We can define the probability of a given event by evaluating, in previous observations, the incidence of the same event under circumstances that are as similar as possible to the circumstances we are observing [this is the frequentistic definition of probability, and is based on the relative frequency of an observed event, observed in previous circumstances (1)]. In other words, probability describes the possibility of an event to occur given a series of circumstances (or under a series of pre-event factors). It is a form of inference, a way to predict what may happen, based on what happened before under the same (never exactly the same) circumstances. Probability can vary from 0 (our expected event was never observed and should never happen) to 1 (or 100%, the event is almost sure). It is described by the following formula: if X = probability of a given x event (Eq. [1]):