What Is a Dependent Variable?

Understanding the difference between dependent and independent variables

Researchers measuring dependent variable
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The dependent variable is the variable that is being measured in an experiment. For example, in a study looking at how tutoring impacts test scores, the dependent variable would be the participants' test scores, since that is what is being measured.

In a psychology experiment, researchers are looking at how changes in the independent variable cause changes in the dependent variable. One way to help identify the dependent variable is to remember that it depends on the independent variable.

When researchers make changes to the independent variable, they then measure any resulting changes to the dependent variable.

For example, if a researcher was looking at how studying influences test scores, the amount of studying would be the independent variable and the test scores would be the dependent variable. The test scores vary based on the amount of studying prior to the test. The researcher could change the independent variable by instead evaluating how age or gender influence test scores.

Observations About the Dependent Variable

In many psychology experiments and studies, the dependent variable is a measure of a certain aspect of a participant's behavior. In an experiment looking at how sleep impacts test performance, the dependent variable would be test performance because it's a measure of the participants' behavior. The independent variable is deemed independent because the experimenters are free to vary it as they need.

The dependent variable is dubbed dependent because it is thought to depend in some way on the variations of the independent variable.

So how do researchers determine what a good dependent variable will be? Stability is often a good sign of a quality dependent variable. If the same experiment is repeated with the same participants, conditions, and experimental manipulations, the effects on the dependent variable should be very close to what they were the first time around.

Examples of Dependent and Independent Variables

  • In a psychology experiment, researchers want to discover if listening to classical music helps students earn better grades on a math exam. In this example, the scores on the math exams are the dependent variable and the classical music is the independent variable.
  • Researchers are interested in seeing how long it takes people to respond to different sounds. In this example, the length of time it takes participants to respond to a sound is the dependent variable, while the sounds are the independent variable.
  • Researchers want to know whether first-born children learn to speak at a younger age than second-born children. In this example, the dependent variable is the age at which the child learns to speak and the independent variable is whether the child is first- or second-born.
  • Researchers are interested in looking at how alcohol use influences reaction times while driving. The amount of alcohol a participant ingests is the independent variable, while their performance on the driving test is the dependent variable.

Sources:

Kantowitz, BH, Roediger, HL, Elmes, DG. Experimental Psychology. Belmont, CA: Wadsworth; 2009.

Weiten, W. Psychology: Themes and Variations. 9th ed. Belmont, CA: Wadsworth; 2013.

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