The number of cars an individual owns is a discrete variable: one can have one, three or five cars, but not 1.4 or 3.8.
Variables are symbols that can acquire different values and that appear in formulas, algorithms, functions and propositions in mathematics and statistics . Depending on their particularities, they are classified differently.
There are random variables , dependent variables , independent variables , qualitative variables , quantitative variables and continuous variables , among others. On this occasion we will refer to discrete variables .
Discrete variable concept
It is interesting to know the etymological origin of the two words that give shape to the term that concerns us now:
-Variable derives from Latin, more precisely from "variabilis" which is the result of the sum of two elements of that language: the verb "variare", which can be translated as "change appearance", and the suffix "-able", which It is used to indicate "possibility."
-Discrete, on the other hand, also comes from Latin. In its case, it is the result of the union of two other components: the prefix "dis-", which is used to specify "separation", and the verb "cernere", which can be translated as "separate" or "sieve".
A discrete variable is one that is capable of taking on values of a given numerical set . That is to say: it only acquires values from a set, not any value.
Between the potentially observable values of a discrete variable there is a distance that is impossible to "complete" with intermediate values. Therefore, between two values there is at least one value that is not observable.
The number of children a woman has is a discrete variable.
Some examples
The number of cars a person owns is a discrete variable. A man can have, for example, one car , two cars or three cars , to name a few possibilities. But you can't have 1.6 cars or 2.8 cars .
In a similar sense, the number of children a woman has is also a discrete variable. You can have 2 , 4 or 6 children , never 2.1 or 5.78 children .
There are many other examples of discrete variables that can be used to understand them. Specifically, among those are the following:
-The gender of the human being, which will be female or male.
-The number of students in a class. And there may be 15, 20 or 30 students, but not 15.3 or 20.8.
-The number of fouls that can be called by the referee in a soccer match.
-The number of radio or television channels you have at home.
-The number of workers that makes up a company's workforce.
Discrete variables vs. continuous variables
On the other hand, continuous variables can acquire any value in an interval, with other intermediate values always existing between two observable values. The existence of more or fewer values depends on the precision of the measurement. For example: a child's height can be 1.2 meters , 1.24 meters or 1.249 meters depending on how it is measured. This implies that certain measurement errors are recorded.
On the contrary, regarding continuous variables, we can use other examples to understand them:
-The weight of a man or a woman.
-The weight of the peaches that have been bought at the market.
-The speed that a car reaches.
-The width of a person's waist.