Читать книгу The Research Experience - Ann Sloan Devlin - Страница 123

A course in research methods exposes you to specific terms that communicate important information. In this chapter, we have already seen important terms, like correlational and quasi-experimental designs. Two critical terms to understand are independent and dependent variable. Often these are referred to as the IV and DV, respectively. An independent variable is manipulated or varied (like our example of art in the previous section). You could think of this as the variable that is independent or “free to differ.” A dependent variable is the outcome of (depends on or is constrained by) exposure to the independent variable. Some researchers look at the independent variable as preceding an effect and, hence, as a cause; the dependent variable reflects the impact of the independent variable and is the outcome or effect.

Independent variable (IV): Variable that is manipulated in an experiment.

Dependent variable (DV): Variable that reflects the impact of the manipulated or independent variable in research.

Quasi-IV: Independent variable (IV) that is naturally occurring (e.g., race and gender) and as a consequence is not assigned at random.

We also need to identify what is called a quasi-IV. You remember that we talked about the difference between quasi-experiments and true experiments (where variables were manipulated and subjects were randomly assigned to condition). Here we will differentiate the parallel terms quasi-IV and “true” IV (normally just referred to as the IV). A quasi-IV is a grouping variable that has not been manipulated (like race or class year). A true IV has been manipulated (like our art example).

As we will see later in this chapter, the statistical analyses for research involving quasi-IVs and IVs are identical; what differs is the language we use to describe the results. When we use quasi-IVs, we use the language of correlation. Thus, if we have sailing team members and nonsailing team members take a cognitive task known as the Mental Rotations Test (MRT; see Vandenberg & Kuse, 1978) and sailing team members score significantly higher than do nonsailing team members on this test, can we state that being a sailing team member caused this higher performance? No. What we can say is that there is a relationship between being a sailing team member and scoring higher on the MRT in comparison to the performance of nonsailing team members.