What is a independent variable?

A independent variable is a variable which stands alone and isn't changed by the other variables in an experiment. In an experiment where the independent variable is changed, the change in the independent variable is expected to directly affect the dependent variable, which is otherwise unaffected by the other variables in the experiment. For example, in an experiment to test the effectiveness of a new herb to treat a medical condition, the independent variable would be the herb and the dependent variable would be the medical condition.

A variable used to explain the variation of the dependent variable. Also called the explanatory variable, the exogenous variable, or the predicting variable.