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What are Independent and Dependent Variables?

By Saul McLeod, updated

Variable are given a special name that only applies to experimental investigations. One is called the dependent variable and the other the independent variable.

The independent variable is the variable the experimenter changes or controls and is assumed to have a direct effect on the dependent variable.

The dependent variable is the variable being tested and measured in an experiment, and is 'dependent' on the independent variable.

In an experiment, the researcher is looking for the possible effect on the dependent variable that might be caused by changing the independent variable.

Independent and Dependent Variables

Independent and Dependent Variable Example

For example, we might change the type of information (e.g. organized or random) given to participants to see what effect this might have on the amount of information remembered.

In this particular example the type of information is the independent variable (because it changes) and the amount of information remembered is the dependent variable (because this is being measured).

Operationalizing Variables

It is very important in psychological research to clearly define what you mean by both your independent and dependent variables.

Operational variables (or operationalizing definitions) refer to how you will define and measure a specific variable as it is used in your study.

For example, if we are concerned with the effect of media violence on aggression, then we need to be very clear what we mean by the different terms. In this case, we must state what we mean by the terms “media violence” and “aggression” as we will study them.

Therefore, you could state that “media violence” is operationally defined (in your experiment) as ‘exposure to a 15 minute film showing scenes of physical assault’; “aggression” is operationally defined as ‘levels of electrical shocks administered to a second ‘participant’ in another room’.

In another example, the hypothesis “Young participants will have significantly better memories than older participants” is not operationalized. How do we define "young", “old” or "memory"? "Participants aged between 16 - 30 will recall significantly more nouns from a list if twenty than participants aged between 55 - 70" is operationalized.

The key point here is that we have made it absolutely clear what we mean by the terms as they were studied and measured in our experiment. If we didn’t do this then it would be very difficult (if not impossible) to compare the findings of different studies into the same behavior.

Operationalization has the great advantage that it generally provides a clear and objective definition of even complex variables. It also makes it easier for other researchers to replicate a study and check for reliability.

How to reference this article:

McLeod, S. A. (2019, Aug 01). What are independent and dependent variables. Simply psychology:

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