The two main variables in an experiment are the independent and dependent variable.

An **independent variable** is the variable that is changed or controlled in a scientific experiment to test the effects on the dependent variable.

A **dependent variable** is the variable being tested and measured in a scientific experiment.

The dependent variable is 'dependent' on the independent variable. As the experimenter changes the independent variable, the effect on the dependent variable is observed and recorded.

## Independent and Dependent Variable Example

For example, a scientist wants to see if the brightness of light has any effect on a moth being attracted to the light. The brightness of the light is controlled by the scientist. This would be the independent variable. How the moth reacts to the different light levels (distance to light source) would be the dependent variable.

## How to Tell the Variables Apart

The independent and dependent variables may be viewed in terms of cause and effect. If the independent variable is changed, then an effect is seen in the dependent variable. Remember, the values of both variables may change in an experiment and are recorded. The difference is that the value of the independent variable is controlled by the experimenter, while the value of the dependent variable only changes in response to the independent variable.

## Remembering Variables With DRYMIX

When results are plotted in graphs, the convention is to use the independent variable as the x-axis and the dependent variable as the y-axis. The DRY MIX acronym can help keep the variables straight:

**D** is the dependent variable**R** is the responding variable**Y** is the axis on which the dependent or responding variable is graphed (the vertical axis)

**M** is the manipulated variable or the one that is changed in an experiment**I** is the independent variable**X** is the axis on which the independent or manipulated variable is graphed (the horizontal axis)

## Independent vs Dependent Variable Key Takeaways

- The independent and dependent variables are the two key variables in a science experiment.
- The independent variable is the one the experimenter controls. The dependent variable is the variable that changes in response to the independent variable.
- The two variables may be related by cause and effect. If the independent variable changes, then the dependent variable is affected.

## Sources

- Carlson, Robert.
*A concrete introduction to real analysis*. CRC Press, 2006. p.183. - Dodge, Y. (2003)
*The Oxford Dictionary of Statistical Terms*, OUP. ISBN 0-19-920613-9 - Everitt, B. S. (2002).
*The Cambridge Dictionary of Statistics*(2nd ed.). Cambridge UP. ISBN 0-521-81099-X.