In every experimental methodology, you got one independent variable, which the researcher manipulates freely and another variable, which then shows the effects of that manipulation. This second variable, which depends on other influences, is called a dependent variable. The following article will include everything you need to know about this topic.
Dependent variables in a nutshell
A dependent variable is the one, whose change you watch during the experiment, meaning it is dependent on other variables.
Definition: Dependent variables
Dependent variables are sometimes also called response variables or outcome variables, as they depict the results being measured in an experiment. It shows the effect, if there is one, which the manipulation of the independent variable had on the test subjects. It is also possible to have more than one dependent variable if your independent one can have different effects.
Example
- Your study examines whether a high stress-level leads to a decline in physical health or not. Therefore, you summon your participants regularly to undergo stressful situations or tests and regularly check their health. The stressful situations would be the independent variable, while the physical health is the dependent variable.
Within the same experiment, you could furthermore measure how stress has an effect on rational thinking by having your participants solve mathematical equations during the stressful situations. This way, you can include a second dependent variable.
Dependent and independent variables
The difference between independent and dependent variables is very simple. They both types of variables are used in scientific experimental context, where one poses the source of a change while the other one depicts its outcome. A researcher usually aims for consistent conditions in an experiment and changes only one thing, the independent variable, in order to observe the effects it has on the test subjects. These results are then measured as the dependent or response variable.
Examples
- Your study is about whether music can relieve stress or not. Therefore, you sample participants with a stressful life and do a survey about their wellbeing before and after a month of listening to music every day. In this case, listening to music or not is the independent variable, while the stress level is the dependent one.
- Another example could be where you assume watering a plant with salty water reduces their growth. In this case, you would water the same type of plant with different concentration of salt to see whether they grow healthily or not. The salt concentration is the independent variable, the growth the dependent variable that shows the results.
Mathematical use
Equations in mathematics pose the simplest example for an independent and dependent variable. Here, the “y” is the dependent variable, as its value depends on the factor “x” on the other side of the term.
Example
For example, if we take the term y=2×x+3
x
1
2
3
4
5
6
7
y
2×1+3=5
2×2+3=7
2×3+3=9
2×4+3=11
2×5+3=13
2×6+3=15
2×7+3=17
Related types of variables
In the experimental context, there are not only independent and dependent variables, but also others that play a role in the outcome.
- Control variables are the consistent factors. In an experiment, it is important that only the independent variable is alternated and everything else stays the same. Therefore, it is necessary to note every other possible influence as a control variable and keep it steady
Example
In the example where the plants’ reactions to different salt concentrations are measured, control variables can be the type of soil used, the light exposure or the amount of water they receive.
- Mediator variables act as an explanation of the relationship between variables and show why and how the explanatory variable influences the results.
Example
In this case, the mediator variable would tell us, why a high salt concentration in the water reduces the growth of plants. This would be because it increases the drainage of water out of the cells, due to the lower concentration of salt inside, but biology is not the subject of interest here.
- Moderator variables, on the other hand, act as an increasing or decreasing force on the relationship of the dependent and independent variables. They can either strengthen the reaction or weaken it, and must therefore be considered in the research design.
Example
A moderator variable in this context could be the type of plant used or the age of the plant. As some plants may have higher tolerance and the tolerance of young plants is usually lower than the one of older ones.
- Extraneous variables are those, which take an influence on the result without being considered. A special type is the confounding variable. These affect the dependent variable and might lead to misinterpretations about the outcome of the study.
Example
A confounding variable could be that the plants kept growing because the water was added with the bottom-up method, meaning that the pot is placed in a bucket of water and the soil sucks up the water by itself. This way, less salt is introduced to the earth and thus to the plant.
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FAQs
Dependent variables could be:
- The result of your exam is dependent on the time you spent on studying. This means that the exam result is the dependent variable and the time spent studying is the independent one.
- Another example might be the correlation between stress and blood pressure. In an experiment, you would measure the blood pressure before and after a stressful situation and see if it changes. The blood pressure is the dependent variable here, the stress the independent one.
- In mathematical equations, “y” is the dependent variable, as its value depends on x and the following solution of the equation.
Yes, this is possible. Sometimes, a researcher inspects the effects of an independent variable on different test subjects with different aims, leading to different dependent variables.
If you have to identify the dependent variable in an experimental context, you just have to identify what it is that the researcher manipulates. Usually, you change one thing in a system and then observe, what and how it changes. This is the independent variable. The effects you then measure are the dependent variable.
