Independent variable

In statistical research, an independent variable is a factor that is being manipulated by the experimenter by controlling the varying amounts (of the IV) to specific individuals in the study.   The dependent variable is measured to determine if the manipulation of the independent variable had any effect. 

The terms "dependent variable" and "independent variable" are used in similar but subtly different ways in mathematics and statistics as part of the standard terminology in those subjects. They are used to distinguish between two types of quantities being considered, separating them into those available at the start of a process and those being created by it, where the latter (dependent variables) are dependent on the former (independent variables).

AKA: predictor variable, controlling variable, manipulated variable, explanatory variable, exposure variable, input variable, the cause and/or a factor.