An Introduction to Research Design

“IV” stands for “independent variable” (also called the “treatment”), “DV” for “dependent variable,” and “EV” for “extraneous variable.” In experimental research we manipulate the IV and observe any resulting change in the DV. Because we are manipulating it experimentally, the IV will probably assume only a very few values, maybe as few as two. The DV may be categorical or may be continuous. The EVs are variables other than the IV which may affect the DV. To be able to detect the effect of the IV upon the DV, we must be able to control the EVs.