When statistic is attended, the probability distributions study and between the most known they have Normal, Binomial Distribution and the Poisson distribution. Each of them with own characteristics, that allow to identify them, including the Binomial distribution can be approximated with the normal distribution. The students, when presenting/displaying the tests have difficulty in identifying generally what Probability distribution must apply to obtain the result. , Perhaps easiest it is the Normal Distribution, because within the statement of the problem there are phrases that they indicate as it is the distribution of the data. A normal distribution is of continuous variates, that mean, that the magnitudes to measure take any real value (example: the amount of rain that falls in Caracas in a month). The Binomial Distribution and the one of Poisson are distributions of discreet variate, that are those that assumes a numerable value group. (Example: the number of students who pass) the statements of the problems of normal distribution, expresses that the data follow the distribution normal and generally gives like data the values of the average and standard deviation, values necessary for the standardization of the variable and to find the probability in the table. Now, to identify a problem of the Binomial Distribution, one is due to observe if the event or experiment has two results; if or no, success or failure, ignition or extinguished; that the events are independent and that the probability remains fixed during the experiment.
Typical statements: probability that man or female is born, to catch a thief, defective pieces. And finally a Poisson distribution describes independent events that happen in a certain space or at a constant speed in the time. It is important to clarify, that the measurement unit is continuous (time, area) but the variate is discreet (number of accident, call numeral) To know clearly the characteristics of the different distributions helps when to solve the problems. I recommend to read several statements and before making any calculation, identifying the characteristics of the distributions.