Independent and Dependent Variables

An independent variable (IV) is a variable that is manipulated by a researcher to investigate whether it consequently brings change in another variable. This other variable, which is measured and predicted to be dependent upon the IV, is therefore named the dependent variable (DV).

For example, in an experiment examining the effect of fatigue on short term memory, there are two groups ‘fatigued’ and ‘non-fatigued’. The fatigued group run for 10 minutes without stopping prior to being tested. Both groups are given a list of words to recall immediately after reading the list.

The independent variable in this example would be fatigued/non-fatigued as it has been manipulated by the experimenter.

The dependent variable would be the number of words recalled off the list because that is how the participants’ performance is measured.

IVs and DVs only occur in experiments, as a cause and effect is predicted between the two (i.e. that changes in the IV will directly lead to changes in the DV).

IVs and DVs do not feature in correlation studies, as correlation studies look for a relationship between co-variables, cause and effect is therefore not established as the variables are predicted to change in response to each other.