In science, a variable is any factor, trait, or condition that can exist in differing amounts or types. Scientists use experiments to search for cause and effect, and variables are the changing quantities that can be altered to test the reaction of another. There are three main types of variables in an experiment:
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Independent Variable: This is the variable that is changed by the scientist, also known as the cause. To ensure a fair test, a good experiment has only ONE independent variable, and it should be something that can be measured quantitatively.
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Dependent Variable: This is the item that responds to the change of the independent variable, also known as the effect. The dependent variable depends/changes when the independent variable is changed. The dependent variable should be something that is observable and measurable.
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Controlled Variable: This is the variable that is kept constant throughout the experiment to ensure that the independent variable is the only factor affecting the dependent variable.
For example, if you were conducting an experiment to test how the amount of water given to plants affects their growth, the independent variable would be the volume of water given to the plants, the dependent variable would be the growth of the plants, and the controlled variables would be factors such as the type of soil, the amount of sunlight, and the temperature.
