The symbol that appears in propositions, algorithms, formulas and functions and that takes on different values is called a variable. According to their characteristics, it is possible to distinguish between different classes of variables.

Quantitative variables are those that take numerical values (i.e. numbers). In this way, they differ from qualitative variables, which express qualities, attributes, categories or characteristics. It is important at this point to know the etymological origin of the two words that form the term in question:

-Variable comes from Latin, specifically derived from “variabilis”, which can be translated as “that can change its appearance”. It is the result of the sum of two components: the verb “variare”, which is synonymous with “change of appearance”, and the suffix “-able”, which is used to indicate possibility.

-Quantitative, in turn, also comes from Latin and is constituted by the union of several elements of that language: “quantum”, which is equivalent to “how much”, and the suffix “-tive”. This is used to record a passive or active relationship.

In the set of quantitative variables, we can also recognize various types of variables. Quantitative continuous variables can take on any value within a certain range. According to the accuracy of the instrument performing the measurement, other values may exist between two values. The height of a person, for example, is a continuous quantitative variable (it can be values like 1.70 meters , 1.71 meters , 1.72 meters , etc.). With respect to continuous quantitative variables, we can establish that other simple examples would be the mass of any object or the height of a building. Discrete quantitative variables, on the other hand, acquire values that separate on the scale. That is: there are no other values among the specific values that the variable acquires. The number of pets a person owns is a discrete quantitative variable: a woman may have 2, 3, or 4 dogs, but never 2.5 or 3.25 dogs. In this case, 2 and 3 are values that the variable can take, with no other possible value between them. Other examples of discrete quantitative variables might be these:

-The number of children a person has.

-The number of animals a farmer owns.

-The set of vehicles that exists in a dealership. Both types of quantitative variables can be combined in a survey or interview. The job seeker can be asked how much he weighs (continuous quantitative variable) and how many children he has (discrete quantitative variable).

In addition to all this, it is important to know another series of interesting data about quantitative variables, such as the following:

-As a general rule, when representing them, we choose to make use of integral diagrams and differential diagrams, which are the ones they use to show the so-called relative frequencies.

-Similarly, you can also use what are bar diagrams.