In an experiment, the factor that is tested is known as the independent variable. This is the variable that the experimenter changes or manipulates to observe its effect. For example, if you are testing how different amounts of sunlight affect plant growth, the amount of sunlight would be the independent variable.
The independent variable is crucial because it helps determine the cause-and-effect relationship in the experiment. By changing this variable and keeping other factors constant, you can observe how it influences the outcome, which is known as the dependent variable.