# Variable Examples

A variable is something that can change or that is inconsistent. In mathematical equations, variables are often represented with letters or symbols to show that they are not a fixed number. In research, there are dependent and independent variables.

In an experiment, the *independent* variable is the variable that is controlled by the researcher. For example, a researcher may control the amount of exercise that he asks participants to perform-30 minutes a day, 1 hour a day, 30 minutes 3 times a week, an hour 3 times a week.

A *dependent* variable is something that depends on how the researcher manipulates the independent variable. For example, if a researcher is controlling how much exercise participants get, he may be interested in changes to their weight, blood pressure, or body composition. These would be *dependent* variables.

In simple terms, if the *independent* variable is manipulated, or changed, then effects will be seen in the *dependent* variable.

A researcher may control how much sunlight plants are given (independent variable) and then measure the growth of the plants (dependent variable).

A researcher may attempt to control how much a child is read to each day (independent variable) and then measure reading proficiency on standardized tests (dependent variable).

A researcher may control the amount of food given to a dog (independent variable) and the dog's weight gain (dependent variable).

A researcher may control the type of math instruction a student is provided with (independent variable) and then measure the student's math proficiency on standardized tests (dependent variable).

A researcher may control the diet of an athlete (independent variable) and then measure athletic performance on a timed run (dependent variable).

A researcher may control the type of cancer treatment a patient receives (independent variable) and then measure the size of tumors on subsequent scans (dependent variable).

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