<P> The control variable ( or scientific constant ) in scientific experimentation is the experimental element which is constant and unchanged throughout the course of the investigation . The control variable strongly influences experimental results , and it is held constant during the experiment in order to test the relative relationship of the dependent and independent variables . The control variable itself is not of primary interest to the experimenter . </P>
what is the purpose of the control variable
in order to test the relative relationship of the dependent and independent variables