Identifying and operationalising independent and dependent variables is a part of experimental research. It is also needed in order to create a hypothesis.

## Independent variable

An independent variable (IV) refers to the manipulated stimuli used to impact the dependent variable. The independent variable is the cause of the change. For example, in an experiment to see how much sleep deprivation impacts attention, the independent variable would be the level of sleep – it is manipulated in order to test attention.

## Dependent variable

Conversely, a dependent variable (DV) refers to the measured outcome. The dependent variable is the effect of the change. That is, its value depends on the manipulation of the independent variable. In the same example as above, the dependent variable would be the level of attention – it is dependent on how much sleep (the independent variable) is granted.

## Operationalization

To operationalize variables, one must indicate how they will be measured. For example, the independent variable (how much sleep is granted) may be in minutes or hours, whilst the dependent variable may be operationalised by performance on a simple arithmetic test.