* Dependent Variable: The variable that is being measured or observed. It changes in response to the independent variable.

* Independent Variable: The variable that is being manipulated or changed by the experimenter.

In this case, you're testing how stirring (the independent variable) affects the speed at which the salt dissolves (the dependent variable). You would measure the time it takes for the salt to dissolve completely in both a stirred and unstirred solution to see the effect of stirring.