What are variables in research? This is a common question among new research students and coaches who plan to read and apply the findings of studies.
A variable is a quality that researchers deal with in their studies. Identifying the variables and how they are measured are important for making realistic applications. For example, if you are interested in finding out to what extent strength levels are related to motivation, then you would have to specify exactly how you plan to measure strength and motivation in your study.
Two common types of variables are easily identified in the title of a research article where the study involves cause and effect—an experiment.
Example: The acute effects of two methods of stretching on vertical jump performance
The independent variable is the one that researchers manipulate. It is the cause of an effect being observed. In experiments, the "effects of" in the title is the clue. In this example, stretching is being manipulated. One group may perform static stretching and another may stretch ballistically. There is probably a control group (maybe more groups) where the participants do not stretch at all before testing their vertical jumps.
The dependent variable is the one being observed. In the title of the study, the word on is the clue to the dependent variable. Vertical jump performance is being measured. Outcomes depend on static stretching.
In some studies, qualities being studied are attributes, such as gender or race. For example, the effect of gender on strength gains, gender is a quality that the participants brought to the study. It was not assigned by the researchers nor could it be manipulated. Gender is an attribute variable, which is also independent in this study.
Confounding variables are those that a researcher fails to control. It plays the role of threaten the internal validity the study. In the stretching study, for example, vertical jump scores could be affected if the equipment used for measuring performance was not calibrated properly for all participants.