Dependent Variable

A dependent variable is the variable measured in an experiment or study; it is affected by the independent variable.

When conducting research, psychologists typically begin with a hypothesis about relationships: if there are two variables, A and B, how does a change in A affect B? An experiment requires two types of variables: independent and dependent. The independent variable is expected to remain unchanged through the experiment, whereas the dependent variable is expected to change as a result of the experimental manipulation. The dependent variable may be changed by the experiment but does not affect the independent variable. For example, an experiment on factors impacting test scores among college students might look at amounts of caffeine consumed in the 12 hours before an exam compared to test scores. While it is possible that caffeine ingested could affect test performance in any direction, test scores cannot affect the amount of caffeine. Test scores would be the independent variable, amount of caffeine would be the dependent variable. The dependent variable must always be measurable and clearly defined.

See also Experimental design ; Experimental psychology ; Hypothesis testing ; Independent variable .

Resources

BOOKS

Montgomery, Douglas C. Design and Analysis of Experiments. New York: John Wiley, 2001.

Privitera, Gregory J. Statistics for the Behavioral Sciences. Thousand Oaks, CA: SAGE, 2012.

Ruxton, Graeme D., and Nick Colegrave. Experimental Design for the Life Sciences. Oxford: Oxford University Press, 2006.

Tamhane, Ajit C. Statistical Analysis of Designed Experiments: Theory and Applications. Hoboken, NJ: Wiley, 2009.

PERIODICALS

Kusurkar, R. A., et al. “Motivation as an Independent and a Dependent Variable in Medical Education: A Review of the Literature.” Medical Teacher 33 (2011): e242–e262.

WEBSITES

abouteducation. “What Is a Dependent Variable?” http://psychology.about.com/od/dindex/g/dependvar.htm (accessed September 17, 2015).

psychanswers.com. “The Dependent Variable and Its Role in Psychology.” http://psych.answers.com/researchmethods/the-dependent-variable-and-its-role-inpsychology (accessed September 17, 2015).