The variable whose value is manipulated in a quantitative scientific experiment. Changes in the independent variable cause changes in the dependent variable.
Example: For workers who are paid by the hour, time worked is the independent variable, because their pay depends on the number of hours worked.
Grinnell, R. (2009). Independent Variable. Psych Central. Retrieved on August 2, 2015, from http://psychcentral.com/encyclopedia/2009/independent-variable/