Dependent and Independent Variables – Concept and examples

We explain what the dependent and independent variables are and the relationship between them. In addition, quantitative and qualitative variables.

independent dependent variables
Body weight is usually a food-dependent variable.

What are the dependent and independent variables?

Variables are symbols that represent some type of quantity or indeterminate factor, that is, it can vary, it is not fixed. It is the opposite, in that sense, to a constant. When they are mathematical symbols, they are usually represented by letters (x, y), but they can also be logical or otherwise.

Among the variables, the independent variables are those that can take various numerical values ​​(or arguments) and are generally represented as x. Independent variables directly affect dependent variables (generally and).

The difference between one and the other has to do with the fact that one depends on the other, and therefore the relationship between the two can be used in a controlled way to study the way in which this dependence occurs. That is, they can be understood as a cause (x) and effect (and), given that the independent variable is in the hands of the researcher, while the other is not.

Let’s try to explain this with an example. If we know that for each hamburger we eat we will have to do two hours of exercise, we can express the relationship between both things mathematically by saying that for each x hamburgers eaten, we will get 2and hours of exercise, since x = 2y.

The independent variable is hamburgers, since we can eat the amount we decide, freely, while the dependent variable will always be the number of hours of exercise, as they follow from the first premise.

Variables of an investigation

continuous independent dependent variables temperature
Temperature is an example of a continuous quantitative variable.

Variables are a fundamental aspect of any investigation or experiment. The way to determine the relationship between the variables that concern us, that is, to propose the beginning of the investigation, is will know as a hypothesis and consists of particular statements.

Apart from what has already been explained about the dependent and independent variables, we can talk about other possible types of variable:

  • Quantitative variables. They are those that represent expressible relationships in terms of quantity, that is, quantifiable, countable. They are classified in discreet (the set of all possible values ​​expressed in isolated points) and continuous (intervals between points or possible values ​​within a range).
  • Qualitative variables. On the contrary, they represent relationships of meaning, property or quality, not numerically expressible. They are classified in turn into nominal (they are used for naming, it has no inherent order or sequence) u ordinal (They obey an ordered series, expressing degrees of the same thing).

Examples of variables

independent dependent variables pollution gases ozone layer
The ozone layer is a variable dependent on toxic gases.

Next we will propose a series of statements in which the independent variables (x) of the dependents (and):

  • The ozone layer in the atmosphere shrinks by a certain amount (y) with each ton of toxic gases emitted monthly (x).
  • Cigarette smoking (x) decreases physical endurance (y).
  • We want to study the impact of yerba mate consumption (x) on the frequency of colon cancer in Uruguayan society (y).
  • Experts affirm an inversely proportional relationship between an individual‘s intelligence (x) and his levels of political fanaticism (y).
  • Scientists suspect that certain types of bacteria reproduce more easily (y) in the presence of some organic alkaloids (x).