ABSTRACT
One of the main objectives of this book is to help students evaluate the quality or merit of a study. Validity is the general term most often used by researchers to judge quality or merit. The term validity is used in several somewhat different ways so we have used modiers to indicate what aspect of validity is being discussed and to help keep the several aspects clear. Four uses of the term validity are shown in Figure 8.1. Notice that research validity is the broadest term and is based on the other three. This chapter discusses causation and internal validity, which are dependent in good part on the type of approach and design, as discussed in Chapter 4 through Chapter 7. Remember that randomized experiments are the most likely to provide evidence that the independent variable caused changes in the dependent variable.
