The variable is a property that can be observed and that can vary, acquire different values ​​and can be measured.

The dependent variable is the "probable effect"; while the independent variable is the "probable cause." The hypothesis, according to Babbie and Davila (2000: 40), arises from theoretical knowledge, not before. It is recommend that the hypothesis be raised when the theoretical framework and methodological design are already defined.

Taking into account the differentiation according to the number of variables that are worked on simultaneously, priority is given to univariables (a single variable) or bivariates (contingency tables, dispersion).