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# What Is a Variable in Science?

## Understanding Variables

It's useful to graph experimental data. The independent variable goes on the x-axis and the dependent variable goes on the y-axis.

Fry Design Ltd, Getty Images

Variables are an important part of science projects and experiments. What is a variable? Basically, a variable is any factor that can be controlled, changed, or measured in an experiment. Scientific experiments have several types of variables. The independent and dependent variables are the ones usually plotted on a chart or graph.

### Types of Variables

• Independent Variable

The independent variable is the one condition that you change in an experiment.

Example: In an experiment measuring the effect of temperature on solubility, the independent variable is temperature.

• Dependent Variable

The dependent variable is the variable that you measure or observe. The dependent variable gets its name because it is the factor that is dependent on the state of the independent variable.

Example: In the experiment measuring the effect of temperature on solubility, solubility would be the dependent variable.

• Controlled Variable

A controlled variable or constant variable is a variable that does not change during an experiment.

Example: In the experiment measuring the effect of temperature on solubility, controlled variable could include the source of water used in the experiment, the size and type of containers used to mix chemicals, and the amount of mixing time allowed for each solution.

• Extraneous Variables
Extraneous variables are "extra" variables that may influence the outcome of an experiment, but aren't taken into account during measurement. Ideally, these variables won't impact the final conclusion drawn by the experiment, but they may introduce error into scientific results. If you are aware of any extraneous variables, you should enter them in your lab notebook. Examples of extraneous variables include accidents, factors you either can't control or can't measure, or factors you consider unimportant. Every experiment has extraneous variables.

Example: You are conducting an experiment to see which paper airplane design flies longest. You may consider the color of the paper to be an extraneous variable. You note in your lab book that different colors of papers were used. Ideally, this variable does not affect your outcome.

### Experiments & Variables

##### Understanding Variables

Anne Marie Helmenstine, Ph.D.