An independent variable is a factor in an experiment that is changed or controlled to test its effects on the dependent variable. It is the variable that researchers manipulate to observe how it influences other variables. For example, in a study examining how light intensity affects plant growth, the light intensity would be the independent variable. In scientific research, identifying the independent variable is crucial for establishing cause-and-effect relationships. By altering the independent variable, scientists can determine if it leads to changes in the dependent variable. This helps in understanding the dynamics of various phenomena in fields like psychology, biology, and physics.