As defined by Maxfield and Earle, variables are “logical groupings of attributes”. (Maxfield and Babbie, 2005: 308 The concepts of “independent variable” and “dependent variable” are used typically when conducting an experiment or a research to determine whether and to what degree a condition or a factor (the independent variable) causes a change or variance in another condition or factor (the dependent variable.) A “variable” is anything that changes. In an experiment that seeks to determine the effect of one variable on another, the independent variable is the one whose effects are measured and the dependent variable is the one on whom these effects are measured against. Indeed, the independent variable may be seen to be the cause and the dependent variable may be considered the effect.
An example to illustrate this point is given. Let us say that in our criminal justice research, we wish to conduct a research to determine whether or not immediate exposure to pornography triggers rape instincts. In this example, the exposure to pornography is the independent variable, and the propensity to commit rape is the dependent variable. We might proceed with our experiment by taking at look at criminals convicted for rape and seeing if they were viewing pornography within a twenty-four hour period before the comission of the crime. Then we would be able to determine if there was a “causation” (Campbell, et. al., 2001: 7.)
It must be noted that one variable can be a dependent variable in one experiment and an independent variable in another experiment. For example, let us look at “drug use” as a variable. In an experiment to determine whether or not drug use leads to domestic violence, drug use is an independent variable. However, in an experiment to determine whether exposure to rock music increases drug use, drug use becomes the dependent variable and exposure to rock music is the independent variable.
Campbell, D., Cook, T., and Shadish, W. (2001). Experimental and Quasi-Experimental Designs for Generalized Causal Inference. New York, NY: Houghton Mifflin Company.
Maxfield, M. and Babbie, E. (2005). Basics of Research Methods for Criminal Justice and Criminology. Belmont, CA: Wadsworth.